Electroless deposition process on a silicide contact

ABSTRACT

Embodiments as described herein provide methods for depositing a material on a substrate during electroless deposition processes, as well as compositions of the electroless deposition solutions. In one embodiment, the substrate contains a contact aperture having an exposed silicon contact surface. In another embodiment, the substrate contains a contact aperture having an exposed silicide contact surface. The apertures are filled with a metal contact material by exposing the substrate to an electroless deposition process. The metal contact material may contain a cobalt material, a nickel material, or alloys thereof. Prior to filling the apertures, the substrate may be exposed to a variety of pretreatment processes, such as preclean processes and activations processes. A preclean process may remove organic residues, native oxides, and other contaminants during a wet clean process or a plasma etch process. Embodiments of the process also provide the deposition of additional layers, such as a capping layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Ser. No. 60/663,493, filed Mar.18, 2005 (9916L), U.S. Ser. No. 60/683,599, filed May 23, 2005(9916L.02), U.S. Ser. No. 60/703,538, filed Jul. 29, 2005 (9916L.03),U.S. Ser. No. 60/703,633, filed Jul. 29, 2005 (9916L.04), U.S. Ser. No.60/709,564, filed Aug. 19, 2005 (9916L.05), U.S. Ser. No. 60/754,230,filed Dec. 27, 2005 (9916L.06), and U.S. Ser. No. 60/731,624, filed Oct.28, 2005 (10659L), which are all herein incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to methods for depositingmaterials on substrates, and more specifically to methods for fillingapertures within a high aspect ratio contact.

2. Description of the Related Art

Multilevel, 45 nm node metallization is one of the key technologies forthe next generation of very large scale integration (VLSI). Themultilevel interconnects that lie at the heart of this technologypossess high aspect ratio features, including contacts, vias, lines, andother apertures. Reliable formation of these features is very importantfor the success of VLSI and the continued effort to increase quality andcircuit density on individual substrates. Therefore, there is a greatamount of ongoing effort being directed to the formation of void-freefeatures having high aspect ratios of 10:1 (height:width) or greater.

Copper and tungsten are choice metals for filling VLSI features, such asa submicron high aspect ratio contact (HARC) on a substrate. Contactsare formed by depositing a conductive interconnect material, such ascopper or tungsten into an aperture (e.g., via) on the surface of aninsulating material disposed between two spaced-apart conductive layers.A high aspect ratio of such an opening may inhibit deposition of aconductive interconnect material to fill an aperture. Although copperand tungsten are popular interconnect materials, deposition processesfor depositing these materials may suffer by forming a void or a seamwithin the contact plug, as illustrated in FIG. 1C.

FIGS. 1A-1B depict a schematic cross-sectional view of an integratedcircuit device on substrate 100 containing aperture 105 formed indielectric layer 104 to expose contact layer 102. During a depositionprocess that may include chemical vapor deposition (CVD) or atomic layerdeposition (ALD), metal layer 106 is deposited on dielectric layer 104and within aperture 105 including on contact layer 102 and the sidewallsof dielectric layer 104 to form plug 103. Near opening 107 of plug 103,metal layer 106 may pinch off, depicted in FIG. 1C, so that plug 103maintains a seam or void 108 therein. During a subsequent chemicalmechanical polishing (CMP) process that removes a portion of metal layer106 and dielectric layer 104 from the surface of substrate 100, void 108may be breached or exposed to form gap 110 within plug 103, asillustrated in FIG. 1D. FIG. 1E depicts conductive layer 112 (e.g.,copper) deposited on substrate 100 forming void 114 by enclosing gap110. Substrate 100 may contain additional layers of material dependingon the overall architecture of the electronic device. For example,dielectric layer 104 may be covered by a barrier layer (not shown)thereon prior to the deposition of conductive layer 112 or conductivelayer 112 may also contain a barrier layer (not shown) thereon prior tothe deposition of layer 120.

Defects, such as a seam or void 114, may cause a series of problemsduring the fabrication of electronic devices depicted herein. Theresistance to current flow through plug 103 is impaired due to the lackof conductive material in void 114. However, a more serious obstacleduring fabrication is the displacement of voids from one layer to thenext. For example, subsequent fabrication processes of substrate 100 mayinclude the deposition of layer 120 (e.g., dielectric layer) onconductive layer 112. During subsequent thermal processing, such as anannealing process, material 116 from conductive layer 112 may diffuseinto void 114 and form void 118 within conductive layer 112. Asillustrated in FIG. 1F, material 116 may not diffuse completely to thebottom of void 114. The defect formed in conductive layer 112, such asvoid 118, will increase the resistance of the circuit containing thedefect and thus affect device performance. Ultimately, the defects inconductive layer 112 can affect the device yield of the fabricatedsubstrate.

Therefore, a need exists for a method to fill a contact level aperturewith a conductive contact material, such that the contact material isdeposited free of voids, seams and other defects.

SUMMARY OF THE INVENTION

Embodiments as described herein provide methods for depositing amaterial on a substrate during electroless deposition processes. In oneembodiment, the substrate contains a contact aperture having an exposedsilicon contact surface. In another embodiment, the substrate contains acontact aperture having an exposed silicide contact surface. Theapertures are filled with a metal contact material by exposing thesubstrate to an electroless deposition process. The metal contactmaterial may contain a cobalt material, a nickel material, or alloysthereof. Prior to filling the apertures, the substrate may be exposed toa variety of pretreatment processes, such as preclean processes andactivations processes. A preclean process may remove organic residues,native oxides, and other contaminants during a wet clean process or aplasma etch process. Embodiments of the process also provide thedeposition of additional layers, such as a capping layer.

In one embodiment, a method for depositing a material on a substrate isprovided which includes positioning a substrate within a processchamber, wherein the substrate has an aperture containing an exposedsilicide contact surface, and exposing the exposed silicide contactsurface to a deposition solution to form a metal contact material overthe exposed silicide contact surface during an electroless depositionprocess. In another embodiment, the substrate has an aperture containingan exposed silicon contact surface, and the method provides forming ametal silicide layer on the exposed silicon contact surface, andexposing the substrate to an electroless deposition process to fill theaperture with a metal contact material. In another embodiment, a metalsuicide layer is formed from the exposed silicon contact surface byexposing the substrate to a metal-containing activation solution. In oneexample, the metal-containing activation solution contains a cobaltsource, a fluoride source, and a hypophosphite source.

In one example, the contact aperture is filled with the metal contactmaterial by continuing the electroless deposition process. The exposedsilicide contact surface may contain at least one metal, such as cobalt,nickel, tungsten, molybdenum, rhenium, titanium, tantalum, hafnium,zirconium, alloys thereof, or combinations thereof. The metal contactmaterial may contain nickel, nickel phosphide, nickel boride, cobalt,cobalt tungsten, cobalt tungsten phosphide, cobalt tungsten boride,cobalt tungsten phosphide boride, cobalt nickel, cobalt phosphide,cobalt boride, cobalt nickel phosphide, cobalt nickel boride,derivatives thereof, alloys thereof, or combinations thereof.

In another embodiment, the exposed silicide contact surface is exposedto a preclean process prior to depositing the metal contact materialthereon. In one example, the substrate is exposed to a plasma to removenative oxides or contaminants from the exposed silicide contact surfaceduring the preclean process. During the plasma etch process, a thin filmmay be formed on the substrate by the plasma and subsequently, the thinfilm is removed by a vacuum sublimation process. The substrate isusually exposed to the plasma along with a process gas. In one example,the process gas contains a gas mixture of ammonia and nitrogentrifluoride. The gas mixture may have a molar ratio of the ammonia tothe nitrogen trifluoride within a range from about 1:1 to about 30:1.

In other embodiments, the substrate is exposed to a wet clean process.In one example, the substrate is exposed to a wet clean solutioncontaining hydrogen fluoride and a basic compound, such as ammoniumhydroxide, tetramethylammonium hydroxide, ethanolamine, diethanolamine,triethanolamine, derivatives thereof, salts thereof, or combinationsthereof. In another example, the wet clean solution contains an EA-HFcomplex, a DEA-HF complex, a TEA-HF complex, a DEA-EA-HF complex, aDEA-TEA-HF complex, a TEA-EA-HF complex, derivatives thereof, saltsthereof, or combinations thereof. In another embodiment, the substrateis exposed to a wet clean solution containing hydrogen peroxide and abasic compound. In another example, the wet clean solution containshydrogen peroxide and hydrogen chloride.

In another embodiment, a method for depositing a material on a substrateis provided which includes positioning a substrate within a processchamber, wherein the substrate has an aperture containing either anexposed silicon contact surface or an exposed silicide contact surface,and the aperture is filled with a cobalt-nickel stack material during anelectroless deposition process. The substrate may be optionally rinsedafter each exposure of the first electroless solution and the secondelectroless solution. Generally, a process cycle of the sequentialexposures of the first and second electroless solutions is repeated toform the metal contact material as a cobalt-nickel stack material havinga predetermined thickness. The electroless deposition process includessequentially exposing the substrate to a first electroless solutioncontaining a cobalt source and to a second electroless solutioncontaining a nickel source. The cobalt-nickel stack material may have afirst layer containing cobalt, cobalt phosphide, cobalt boride, cobalttungsten, cobalt tungsten phosphide, cobalt tungsten boride, cobalttungsten phosphide boride, derivatives thereof, alloys thereof, orcombinations thereof, and a second layer containing nickel, nickelphosphide, nickel boride, derivatives thereof, alloys thereof, orcombinations thereof.

In one embodiment, a capping layer is deposited on the exposed silicidecontact surface prior to filling the aperture with the metal contactmaterial. The capping layer may contain cobalt tungsten phosphide,cobalt tungsten boride, cobalt tungsten phosphide boride, derivativesthereof, alloys thereof, or combinations thereof. The capping layer maybe formed or deposited by a vapor deposition process, but preferably isdeposited during an electroless deposition process. In anotherembodiment, a self assembled monolayer (SAM-layer) may be depositedwithin the aperture prior to depositing the metal contact material.

In one embodiment, a composition of a cobalt deposition solution isprovided which contains a cobalt source at a concentration within arange from about 1 mM (millimolar, millimole/L) to about 150 mM, areducing agent source at a concentration within a range from about 1 mMto about 100 mM, and a chelating agent source at a concentration withina range from about 10 mM to about 500 mM. In another example, the cobaltdeposition solution contains the cobalt source at a concentration withina range from about 10 mM to about 100 mM, the reducing agent source at aconcentration within a range from about 5 mM to about 50 mM, and thechelating agent source at a concentration within a range from about 50mM to about 300 mM. In another example, the cobalt deposition solutioncontains the cobalt source at a concentration within a range from about20 mM to about 80 mM, the reducing agent source at a concentrationwithin a range from about 10 mM to about 40 mM, and the chelating agentsource at a concentration within a range from about 75 mM to about 250mM. In another example, the cobalt deposition solution contains thecobalt source at a concentration of about 35 mM, the reducing agentsource at a concentration of about 25 mM, and the chelating agent sourceat a concentration of about 150 mM. The chelating agent source mayinclude citric acid, lactic acid, glycine, ethanolamine, diethanolamine,triethanolamine, salts thereof, derivatives thereof, or combinationsthereof. In one example the reducing agent source comprisesdimethylamine-borane complex. Other examples provide that thecomposition contains boric acid, saccharin, ammonium fluoride, ortetramethylammonium fluoride. A pH adjusting agent, such as TMAH, may beadded to provide the cobalt deposition solution having a pH value withina range from about 8 to about 10, such as about 9.2.

In another embodiment, a composition of a nickel deposition solution isprovided which contains a nickel source at a concentration within arange from about 1 mM to about 150 mM, a reducing agent source at aconcentration within a range from about 1 mM to about 150 mM, and achelating agent source at a concentration within a range from about 10mM to about 500 mM. In another example, the nickel deposition solutioncontains the nickel source at a concentration within a range from about5 mM to about 100 mM, the reducing agent source at a concentrationwithin a range from about 5 mM to about 100 mM, and the chelating agentsource at a concentration within a range from about 50 mM to about 300mM. In another example, the nickel deposition solution contains thenickel source at a concentration within a range from about 10 mM toabout 80 mM, the reducing agent source at a concentration within a rangefrom about 10 mM to about 80 mM, and the chelating agent source at aconcentration within a range from about 75 mM to about 200 mM. Inanother example, the nickel deposition solution contains the nickelsource at a concentration of about 40 mM, the reducing agent source at aconcentration of about 40 mM, and the chelating agent source at aconcentration of about 150 mM. The chelating agent source may includecitric acid, lactic acid, glycine, ethanolamine, diethanolamine,triethanolamine, salts thereof, derivatives thereof, or combinationsthereof. In one example the reducing agent source comprisesdimethylamine-borane complex. Other examples provide that thecomposition contains boric acid. A pH adjusting agent, such as TMAH, maybe added to provide the nickel deposition solution having a pH valuewithin a range from about 8 to about 10, such as about 9.2.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the inventionare attained and can be understood in detail, a more particulardescription of the invention, briefly summarized above, may be had byreference to the embodiments thereof which are illustrated in theappended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

FIGS. 1A-1F illustrate schematic cross-sectional views of an integratedcircuit formed by a process described in the art;

FIGS. 2A-2F illustrate schematic cross-sectional views of integratedcircuits formed by deposition processes described within embodimentsherein;

FIGS. 3A-3Q illustrate schematic cross-sectional views of integratedcircuits formed by other deposition processes described withinembodiments herein;

FIGS. 4A-4H illustrate schematic cross-sectional views of integratedcircuits formed by another deposition process described withinembodiments herein;

FIG. 5 illustrates a flow chart depicting a process sequence asdescribed within embodiments herein;

FIG. 6 illustrates a flow chart depicting another process sequence asdescribed within embodiments herein;

FIG. 7 illustrates a flow chart depicting another process sequence asdescribed within embodiments herein;

FIG. 8 illustrates a flow chart depicting an electroless depositionprocess as described within embodiments herein;

FIGS. 9A-9D illustrate a schematic representation of timing sequencesfor electroless deposition processes as described within embodimentsherein;

FIG. 10 illustrates a flow chart depicting an electroless depositionprocess as described within embodiments herein; and

FIG. 11 illustrates a schematic representation of an alternative timingsequence for an electroless deposition process as described within anembodiment herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments as described herein provide methods for depositing amaterial on a substrate during electroless deposition processes. In oneembodiment, the substrate contains a contact aperture having an exposedsilicon contact surface. In another embodiment, the substrate contains acontact aperture having an exposed silicide contact surface. Theapertures are filled with a metal contact material by exposing thesubstrate to an electroless deposition process. The metal contactmaterial may contain a cobalt material, a nickel material, and alloysthereof. Prior to filling the apertures, the substrate may be exposed toa variety of pretreatment processes, such as preclean processes andactivations processes. A preclean process may remove organic residues,native oxides, and other contaminants during a wet clean process or aplasma etch process. Embodiments of the process also provide thedeposition of additional layers, such as a capping layer.

Metal-Containing Interconnect Processes

FIG. 2A illustrates a cross-sectional view of substrate 200 havingaperture 210 formed into dielectric layer 204. Aperture 210 may includefeatures, such as contact holes, vias, or trenches. Dielectric layer 204contains an insulating material that includes silicon oxide, siliconnitride, silicon on insulator (SOI), silicon oxynitride, fluorine-dopedsilicate glass (FSG), or carbon-doped silicon oxides, such asSiO_(x)C_(y), for example, BLACK DIAMOND® low-k dielectric, availablefrom Applied Materials, Inc., located in Santa Clara, Calif.

Aperture 210 may be formed in dielectric layer 204 using conventionallithography and etching techniques to expose interconnect layer 202,such as a bit line layer. Interconnect layer 202 contains a conductivemetal such as copper, tungsten, aluminum or alloys thereof. Oxidesurface 212 is usually formed upon the oxidation of interconnect layer202 subsequent to etching and ashing processes used to form aperture210. Oxide surface 212 may be a continuous or a discontinuous layeracross the surface of interconnect layer 202 and includes a surfaceterminate with oxygen, hydrogen, hydroxides, metals, or combinationsthereof. In this configuration, interconnect layer 202 may contain oxidesurface 212.

FIGS. 2A-2C illustrate cross-sectional views of an electronic device atdifferent stages of an interconnect fabrication sequence incorporatingone embodiment of the invention for pre-treating and subsequentlyfilling aperture 210 with a nickel-containing material or acobalt-tungsten alloy. FIG. 2B illustrates substrate 200 after exposingoxide surface to a pretreatment process. Contact surface 214 ofinterconnect layer 202 is exposed and is free of or substantially freeof oxide surface 212. In one aspect, oxide surface 212 may be chemicallyreduced to a tungsten metal. For example, oxide surface 212 is exposedto a hydrogen plasma to remove the oxygen and form an oxide free contactsurface 214. In another example, oxide surface 212 may be exposed to avapor deposition process containing diborane to remove oxygen and formcontact surface 214 containing tungsten boride. In another aspect, oxidesurface 212 is exposed to a wet clean process to further oxidize andremove tungstate ion while leaving behind a clean contact surface 214.Additives, such as surface chelators, may be used within the wet cleansolution that adhere to the freshly prepared contact surface 214 andprohibit excess oxidization.

A plasma pretreatment process may be conducted for a predetermined timeto reduce oxide surface 212, leaving a substantially oxide-free contactsurface 214. A plasma pretreatment process may occur for about 5 minutesor less, preferably, within a range from about 1 second to about 60seconds, more preferably, from about 5 seconds to about 30 seconds.During the pretreatment process, the substrate is maintained at atemperature within a range from about 20° C. to about 150° C.,preferably, from about 50° C. to about 100° C. The process chamber mayhave a pressure within a range from about 0.1 Torr to about 450 Torr,preferably, from about 1 Torr to about 100 Torr, and more preferably,from about 10 Torr to about 30 Torr.

The plasma treatment process may be conducted in a process chambercapable of plasma vapor deposition techniques. For example, thesubstrate may be placed into a plasma enhanced ALD (PE-ALD), a plasmaenhanced CVD (PE-CVD) or high density plasma CVD (HDP-CVD) chamber, suchas the ULTIMA HDP-CVD®, available from Applied Materials, Inc., locatedin Santa Clara, Calif. An inductively coupled plasma generating device,capacitively coupled plasma generating device, or combination thereofmay be used in a plasma chamber to carryout the plasma treatmentprocess.

Oxide surface 212 may be exposed to a reducing plasma containing thereductant to form a substantially oxide-free contact surface 214. Thereductant may be diluted in a carrier gas and includes hydrogen,diborane, silane, disilane, phosphine, derivatives thereof, orcombinations thereof. During the plasma pretreatment process, a carriergas flow is established within the process chamber and exposed to thesubstrate. Carrier gases may be selected so as to also act as a purgegas for the removal of volatile reactants and/or by-products from theprocess chamber. Carrier gases or purge gases include helium, argon,hydrogen, forming gas, or combinations thereof. The carrier gas may beprovided at a flow rate within a range from about 500 sccm to about5,000 sccm, preferably, from about 500 sccm to about 2,500 sccm. Thereductant may be provided at a flow rate within a range from about 5sccm to about 500 sccm, preferably, from about 10 sccm to about 100sccm. The plasma may be formed using an RF power delivered to the plasmagenerating devices (e.g., showerhead in a capacitively coupled chamberor a substrate support) utilized in the plasma chamber where the RFpower ranges from about 100 W to about 10,000 W at an RF frequencybetween about 0.4 kHz and about 10 GHz. In one aspect, the plasma isformed using a showerhead RF power setting and a substrate support RFpower setting that is within a range between about 500 W and about 5,000W at a frequency of about 13.56 MHz.

In an exemplary plasma pretreatment process, the substrate is heated toabout 50° C. and the process chamber is maintained at a pressure ofabout 10 Torr, to reduce the oxides formed on contact surface 214. Thesubstrate may be exposed to a reducing plasma containing hydrogen at aflow rate of about 1,000 sccm for a time period of about 30 seconds toremove oxide layer 212.

In another exemplary plasma pretreatment process, a substrate is heatedto about 50° C., the process chamber is maintained at a pressure ofabout 10 Torr using a flow rate of about 50 sccm of diborane and about450 sccm of a helium carrier gas to reduce the oxides formed on contactsurface 214. The substrate is exposed to the reducing plasma for about30 seconds to remove the oxide layer 212.

In another embodiment, the pretreatment process may be a liquidreduction process, whereas oxide surface 212 is exposed to a reducingsolution to form contact surface 214. The reducing solutions may containat least one metal-reductant, such as a compound containing avariable-valence metal. Variable-valence metals are utilized asmetal-reductants due to the availability of electrons between redoxstates and include compounds of Ti³⁺/Ti⁴⁺, Fe²⁺/Fe³⁺, Cr²⁺/Cr³⁺ andSn²⁺/Sn⁴⁺. Metal-reductants containing variable-valence metals maycontain a variety of anionic ligands including complexing agents andhalides, such as chlorides, fluorides, bromides or iodides. Complexingagents that are useful may have functional groups that includecarboxylic acids, dicarboxylic acids, polycarboxylic acids, amino acids,amines, diamines, polyamines, alkylamines, alkanolamines andalkoxyamines. Complexing agents may include citric acid, glycine,ethylenediamine (EDA), monoethanolamine, diethanolamine (DEA),triethanolamine (TEA), derivatives thereof, salts thereof orcombinations thereof. In one embodiment, citric acid or a citrate saltis a preferred complexing agent within a reducing solution. For example,a reducing solution may contain titanium salts with carboxylic acidligands, such as a citrate.

Generally, the reducing solutions are formed in water by combining ametal halide (e.g., titanium chloride containing TiCl₃ and TiCl₄) with asalt containing a predetermined ligand (e.g., trisodium citrate) to forma metal complex or a metal salt that contains the predetermined ligand(e.g., titanium citrate) having a variable-valence state. The reducingsolution may further contain additives such as various chelators,surfactants, pH adjusting agents, or combinations thereof.Variable-valence metal compounds and reducing solutions are furtherdescribed in V. V. Sviridov et al., “Use of Ti(III) Complexes to reduceNi, Co, and Fe in Water Solution,” J. Phys. Chem., vol. 100, pp.19632-19635, (1996), M. Majima et al., “Development of Titanium RedoxElectroless Plating Method,” SEI Technical Review, vol. 54, pp. 67-70,(June 2002), S. Nakao et al., “Electroless Pure Nickel Plating Processwith Continuous Electrolytic Regeneration System,” Surface and CoatingsTechnology, vols. 169-170(1), pp. 132-134., (Jun. 2, 2003), which areeach incorporated by reference to the extent not inconsistent with theclaimed aspects and description herein.

In an effort to remove oxide surface 212, substrate 200 is exposed to areducing solution for a predetermined time to remove the oxides fromcontact surface 214. The liquid reduction process may occur for about 5minutes or less, preferably within a range from about 1 second to about120 seconds, more preferably, from about 5 seconds to about 90 seconds.During the liquid reduction process, the substrate is heated to atemperature within a range from about 20° C. to about 150° C.,preferably, from about 50° C. to about 100C.

In another embodiment, the pretreatment process may be a vapordeposition process, whereas oxide surface 212 is exposed to a reducingvapor to form contact surface 214. The reductant may include borane,diborane, borane-alkylsulfides, such as borane-dimethylsulfide(BH₃.(CH₃)₂S), alkyboranes (e.g., ethylborane), phosphine,alkylposphines (e.g., dimethylphosphine), silane, disilane, trisilane,alkylsilanes (e.g., methylsilane), ammonia, hydrazine, hydrogen,derivatives thereof, or combinations thereof. Preferably, the reductantis diborane, phosphine, silane, hydrazine, hydrogen, or combinationsthereof.

In an effort to remove the oxide surface 212 the substrate 200 isexposed to a reducing vapor process for a predetermined time to removethe oxides from the contact surface 214. The reducing vapor process mayoccur for about 5 minutes or less, preferably within a range from about1 second to about 120 seconds, more preferably, from about 5 seconds toabout 90 seconds. During the reducing vapor process, the substrate ismaintained at a temperature within a range from about 20° C. to about150° C., preferably, from about 50° C. to about 100° C. The processchamber may have a pressure within a range from about 0.1 Torr to about450 Torr, preferably, from about 1 Torr to about 100 Torr, and morepreferably, from about 10 Torr to about 30 Torr.

In one aspect, the reductant used to remove oxide layer 212 may bediluted in a carrier gas. During the reducing vapor process, a carriergas flow is established within the process chamber and exposed to thesubstrate. Carrier gases may be selected so as to also act as a purgegas for the removal of volatile reactants and/or by-products from theprocess chamber. Carrier gases or purge gases include helium, argon,nitrogen, hydrogen, forming gas, mixtures thereof. The carrier gas maybe provided at a flow rate within a range from about 100 sccm to about5,000 sccm, preferably, from about 500 sccm to about 2,500 sccm. Thereductant may be provided at a flow rate within a range from about 5sccm to about 500 sccm, preferably, from about 10 sccm to about 100sccm.

The reducing vapor process may be conducted in a process chamber capableof vapor deposition, such as an ALD process chamber or a CVD processchamber. A process chamber useful for ALD during the reducing vaporprocess is described in commonly assigned U.S. Pat. Nos. 6,916,398 and6,878,206, which are both incorporated herein by reference.

In another embodiment, oxide surface 212 is removed by further oxidizingby a wet clean process which includes dispensing a wet clean solutionacross or sprayed on the surface of substrate 200. The wet clean processmay be an in situ process performed in the same processing cell as asubsequent electroless deposition process. Alternatively, substrate 200may be wet cleaned in a separate processing cell from the subsequentelectroless deposition processing cell. The wet clean process usuallyincludes an acidic wet clean solution with a pH of about 4 or less,preferably, within a range from about 1.5 to about 3. Oxide surface 212having a tungsten oxide typically requires an aggressive cleaning at lowpH values. The pH value of the wet clean solution is usually adjusted byadding an acid or a base to the predetermined value. The acid mayinclude hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,derivatives thereof, or combinations thereof. The base may include ahydroxide salt, ammonia or an amine, such as ethanolamine (EA),diethanolamine (DEA), triethanolamine (TEA), derivatives thereof, saltsthereof, or combinations thereof. The wet clean solution also containsat least one chelator or complexing agent, such as a carboxylic acid orcarboxylate, for example, a citrate, oxalic acid, glycine, saltsthereof, or combinations thereof. In one example, the wet clean solutioncontains about 0.05 M to about 0.5 M of citric acid and optionally up toabout 0.25 M of methanesulfonic acid.

Once oxide surface 212 is removed or reduced to reveal contact surface214 by the processes described herein, fill material 220 may bedeposited thereon. FIG. 2C illustrates substrate 200 after fill material220 has been deposited on contact surface 214. Fill material 220 iscomposed of a conductive material and preferably deposited by anelectroless deposition process. A conductive material deposited as fillmaterial herein includes nickel, cobalt, tungsten, cobalt-tungstenalloys, alloys thereof, or combinations thereof. In one example, fillmaterial 220 is a nickel-containing layer deposited by an electrolessdeposition solution. In another example, fill material 220 is acobalt-containing layer (e.g., CoW-alloy) deposited by an electrolessdeposition solution.

In an alternative embodiment, FIGS. 2A, 2D-2F illustrate cross-sectionalviews of an electronic device at different stages of an interconnectfabrication sequence to pretreat and subsequently fill aperture 210 witha conductive material. Nickel or cobalt-tungsten alloys are used asconductive materials to fill aperture 210. FIG. 2D illustrates substrate200 after a pretreatment process has been performed on the oxide surface212. In one aspect of the pretreatment process a ruthenium oxide layer216 is deposited by exposing substrate 200 and oxide surface 212 to aruthenium tetroxide (RuO₄) vapor. Thereafter, ruthenium oxide layer 216may be chemically reduced to form ruthenium-containing layer 218 onoxide surface 212, as illustrated in FIG. 2E.

A ruthenium containing layer may be deposited on the substrate by use ofa vapor deposition process, such as an in situ generated process, or ina liquid deposition process, such as an aqueous solution or suspension.Preferably, ruthenium tetroxide is generated in situ by exposing aruthenium-containing source to an oxidizing gas prior and exposing theproduct to oxide surface 212. Ruthenium tetroxide is a strong oxidantand therefore readily reacts with any exposed metal oxide (e.g.,tungsten oxide) layers to form a consistent and catalytic active layerof ruthenium oxide.

In one example of forming ruthenium tetroxide, ozone gas is produced bysupplying an oxygen source gas into an ozone generator. The oxygensource may include oxygen (O₂), nitrous oxide (N₂O), nitric oxide (NO),nitrogen dioxide (NO₂), or combinations thereof. Preferably, a 12 vol %ozone is generated by flowing oxygen through the ozone generator. Theoxidizing gas containing ozone may be purified when passed or bubbledthrough a silicon gel. Subsequently, the ozone is exposed to a metallicruthenium source to form ruthenium tetroxide that is condensed in acooled cold trap. The ozone flow is stopped and the cold trap is purgedwith an inert gas (e.g., nitrogen) to rid the line of excess oxygen.Thereafter, the cold trap is warmed to a temperature to sublime theruthenium tetroxide while a flow of inert gas is passed therethrough.The vaporized ruthenium tetroxide saturates the inert gas to form adeposition gas.

In an exemplary vapor deposition process, a deposition gas containingruthenium tetroxide is delivered to a substrate having a tungsten oxidelayer formed thereon. During the process, the substrate is maintained ata temperature of about 100° C. After exposing oxide surface 212 to theruthenium tetroxide containing gas for about 30 seconds, ruthenium oxidelayer 216 is formed on the tungsten oxide layer.

Ruthenium oxide layer 216 may be exposed to a reductant formingruthenium-containing layer 218. The ruthenium oxide is chemicallyreduced to ruthenium metal. For example, ruthenium oxide layer 216 maybe exposed to a hydrogen plasma to remove the oxygen and form metallicruthenium-containing layer 218. In another example, ruthenium oxidelayer 216 may be exposed to a vapor deposition process containingdiborane to remove oxygen and form ruthenium-containing layer 218containing ruthenium boride. In another example, ruthenium oxide layer216 is exposed to phosphine through a vapor deposition process to removeoxygen and form ruthenium-containing layer 218 containing rutheniumphosphide.

Fill material 220 may be deposited on ruthenium-containing layer 218 tofill aperture 210 as illustrated in FIG. 2F. Fill material 220 containsnickel or a cobalt-tungsten alloy. The electroless deposition processand the composition of fill material 220 are previously described abovefor substrate 200 depicted in FIG. 2C.

Silicon-Containing Interconnect Processes

FIGS. 3A-3Q and 4A-4H illustrate cross-sectional views of electronicdevices disposed on substrates 300 and 400 at different stages ofinterconnect fabrication sequences incorporating multiple embodimentsherein. FIGS. 5-7 provide flow charts of processes 500, 600, and 700that may be used to form substrates 300 and 400 while correlating withFIGS. 3A-3Q and 4A-4H. Processes 500, 600, and 700 may be used duringinterconnect fabrication where an exposed contact surface containseither a silicon surface or a silicide surface on substrates 300 and400.

FIG. 3A illustrates a cross-sectional view of substrate 300 havingcontact aperture 310 formed within dielectric layer 304. Dielectriclayer 304 contains an insulating material that may include silicondioxide and other silicon oxides, silicon on insulator (SOI), siliconoxynitride, fluorine-doped silicate glass (FSG), or carbon-doped siliconoxides, such as SiO_(x)C_(y), for example, BLACK DIAMOND® low-kdielectric, available from Applied Materials, Inc., located in SantaClara, Calif. Contact aperture 310 may be formed in dielectric layer 304using conventional lithography and etching techniques to exposeinterconnect layer 302, such as a bit line layer. Alternatively,dielectric layer 304 may be deposited on interconnect layer 302 formingcontact aperture 310 therein. Interconnect layer 302 may contain puresilicon or a silicon-containing material that contains germanium,carbon, boron, phosphorous, arsenic, metals, or combinations thereof,among other dopants. For example, interconnect layer 302 may containsilicon, silicon carbide, silicon germanium, silicon germanium carbide,metal silicide, doped variants thereof, or combinations thereof. In oneexample, interconnect layer 302 is a MOS type source or a draininterface and is generally a doped (e.g., n+ or p+) silicon region ofsubstrate 300.

Oxide surface 312 is usually formed upon the oxidation of interconnectlayer 302 during an exposure to air subsequent to etching and ashingprocesses used forming contact aperture 310. Oxide surface 312 may be acontinuous layer or a discontinuous layer across the surface ofinterconnect layer 302 and include a surface terminations of oxygen,hydrogen, hydroxide, halide, metals, or combinations thereof. Oxidesurface 312 may also contain various contaminants, such as organic andinorganic residues and particulate. Oxide surface 312 formed oninterconnect layer 302 generally contains a metastable lower qualityoxide (e.g., SiO_(x), where x is between 0 and 2) compared to the muchmore stable oxide materials that are typically used to form dielectriclayer 304 (e.g., SiO₂), such as thermal oxides. The metastable lowerquality oxide (e.g., the “native oxide”) is much easier to remove frominterconnect layer 302 than dielectric layer 304, probably due to alower activation energy than the material of dielectric layer 304.

FIG. 3B illustrates substrate 300 containing exposed surface 314 oninterconnect layer 302 subsequent to the removal of oxide surface 312.Exposed surface 314 may be formed by at least one pretreatment processduring steps 510, 610, or 710 of processes 500, 600, or 700, asdescribed by embodiments herein. In some embodiments, exposed surface314 may contain an exposed silicon contact surface. In otherembodiments, exposed surface 314 may contain an exposed silicide contactsurface.

During steps 510, 610, or 710, substrate 300 may be exposed to at leastone pretreatment process, such as a preclean process, an activationprocess, or combinations thereof for forming exposed surface 314. Apreclean process may be used to remove oxide surface 312 and reveal asilicon surface or a suicide surface of exposed surface 314. In oneembodiment, the preclean process may be a wet clean process, such as abuffered oxide etch (BOE) process, a SC1 process, a SC2 process, or aHF-last process. Alternatively, the preclean process may be a dry cleanprocess, such as a plasma etch process. For example, a plasma etchprocess that may be used during a preclean process is the SICONI™preclean process, available from Applied Materials, Inc., located inSanta Clara, Calif. Pretreatment processes, such as a preclean processand an activation process for forming exposed surface 314, are furtherdescribed below.

An activation process may also be used as a pretreatment process to formexposed surface 314. In one embodiment, substrate 300 is exposed to anactivation solution containing a cobalt source, a fluoride source, and ahypophosphite source to transform oxide surface 312 to a metal silicidesurface of exposed surface 314. In another embodiment, substrate 300 isexposed to an activation solution containing a variable-valence metalreducing agent that chemically reduces oxide surface 312 to a siliconsurface of exposed surface 314. In another embodiment, substrate 300 isexposed to reducing hydrogen plasma that chemically reduces oxidesurface 312 to a silicon surface of exposed surface 314.

In one embodiment, FIGS. 3B-3C illustrate substrate 300 before and aftercontact aperture 310 is filled with metal contact material 320, duringsteps 560, 660, or 760 of processes 500, 600, or 700 (FIGS. 5-7), asdescribed by embodiments herein. Metal contact material 320 may bedeposited on exposed surface 314 of interconnect layer 302 withincontact aperture 310. Metal contact material 320 is usually deposited onexposed surface 314 during an electroless deposition process tobottom-up fill contact aperture 310. In one example, the electrolessdeposition process is continued until aperture 310 is filled with metalcontact material 320.

Alternatively, a second electroless deposition process, or multipledeposition processes, may be used to form metal contact material 320while filling contact aperture 310. For example, metal contact material320 may be formed of different materials to vary the compositionthroughout, such as a graded material. In an alternative embodiment,cobalt-nickel stack material 330 is formed of at least two types ofmaterials sequentially deposited on each other, such as layers 322 and324, as illustrated in FIGS. 4A and 4B by substrate 400 that correlatesto substrate 300 in FIGS. 3C and 3D. In one example, layer 322 maycontain a cobalt material and layer 324 may contain a nickel material.In another example, layer 322 may contain a nickel material and layer324 may contain a cobalt material.

Metal contact material 320 may be formed or deposited during electrolessdeposition process described herein. The composition of metal contactmaterial 320 may vary based on the particular electronic devicerequirements. Metal contact material may contain metallic nickel, nickelphosphide, nickel boride, nickel phosphide boride, metallic cobalt,cobalt phosphide, cobalt boride, cobalt phosphide boride, cobalttungsten, cobalt tungsten phosphide, cobalt tungsten boride, cobalttungsten phosphide boride, cobalt nickel, cobalt nickel phosphide,cobalt nickel boride, cobalt nickel phosphide boride, silicides thereof,derivatives thereof, alloys thereof, or combinations thereof.Electroless deposition processes and solutions for forming or depositingmetal contact material 320 and cobalt-nickel stack material 330, arefurther described below.

FIG. 3D illustrates silicide layer 315 at the interface of exposedsurface 314 and metal contact material 320. Silicide layer 315 may beformed by exposing substrate 300 to an optional thermal process duringsteps 580, 680, or 780. Silicide layer 315 may contain a cobaltsilicide, nickel silicide, cobalt tungsten silicide, cobalt nickelsilicide, borides thereof, alloys thereof, derivatives thereof, orcombinations thereof. Silicide layer 315 may be formed prior, during, orafter filling of aperture 310 with metal contact material 320. In oneexample, substrate 300 is heated during a thermal process to formsilicide layer from silicon atoms of exposed surface 314 and metal atomsof metal contact material 320. Generally, substrate 300 may be heated toa temperature within a range from about 150° C. to about 500° C. for atime period within a range from about 5 seconds to about 10 minutes.

In another embodiment, FIGS. 3B and 3E-3G illustrate substrate 300 atdifferent stages of process 500. SAM-layer 350 may be formed onsubstrate 300 during optional step 550, as depicted in FIG. 3E.SAM-layer 350 may be initially deposited over dielectric layer 304 andexposed surface 314. In one example, SAM-layer 350 is deposited onexposed surface 314 containing an exposed contact silicon surface. Inanother example, SAM-layer 350 is deposited on exposed surface 314containing an exposed contact silicide surface.

FIGS. 3E-3F illustrate substrate 300 before and after contact aperture310 is filled with metal contact material 320, during step 560 ofprocess 500 (FIG. 5). Metal contact material 320 is deposited onSAM-layer 350 within contact aperture 310. Metal contact material 320 iswith interconnect layer 302. In one example, substrate 300 may beexposed to a thermal process to form silicide layer 315 (FIG. 3G).Silicide layer 315 provides higher electrical conductivity, than withoutsilicide layer 315, at the interface between interconnect layer 302 andmetal contact material 320. In an alternative embodiment, cobalt-nickelstack material 330 may be formed on SAM-layer 350, as illustrated inFIG. 4C by substrate 400 that correlates to substrate 300 in FIG. 3G.Deposition processes for depositing SAM-layer 350 on substrate 300 arefurther described below.

FIG. 6 depicts a flow graph of process 600 containing steps 610, 650,660, and 680 that correlate to steps 510, 550, 560, and 580 of process500. However, process 600 further provides the formation or depositionof a suicide material during step 620. In one embodiment of process 500,a silicide material may be formed during a pretreatment process at step510. For example, substrate 300 may be exposed to a clean process toremove oxides and contaminants and subsequently exposed to an activationprocess to form a silicide material.

FIG. 3H depicts substrate 300 containing metal-containing layer 316disposed on interconnect layer 302 within contact aperture 310.Metal-containing layer 316 may contain a metal, a metal silicide, or analloy thereof. Metal-containing layer 316 may be formed or depositedduring steps 510, 610, 620, 710, or 720 and include a metal layer or ametal silicide layer. In one example, metal-containing layer 316contains a metallic layer and is deposited on exposed surface 314containing an exposed contact silicon surface. Thereafter, exposedsurface 314 and metal-containing layer 316 form a metal silicide duringa thermal process. In another example, metal-containing layer 316contains a metal suicide material deposited or formed on exposed surface314. In another example, metal-containing layer 316 contains a metalsilicide material formed either prior to or during steps 620 or 720.

In one embodiment, metal-containing layer 316 contains a cobaltmaterial, such as metallic cobalt, cobalt silicide, cobalt phosphide,cobalt boride, cobalt phosphide boride, cobalt tungsten, cobalt tungstenphosphide, cobalt tungsten boride, cobalt tungsten phosphide boride, acobalt alloy, suicides thereof, or combinations thereof. In anotherembodiment, metal-containing layer 316 contains a cobalt nickelmaterial, such as cobalt nickel, cobalt nickel phosphide, cobalt nickelboride, derivatives thereof, alloys thereof, or combinations thereof. Inanother embodiment, metal-containing layer 316 contains a nickelmaterial, such as metallic nickel, nickel silicide, nickel phosphide,nickel boride, nickel phosphide boride, a nickel alloy, or combinationsthereof. In other embodiments, the exposed silicide contact surface maybe metal-containing layer 316 that contains at least one metal, such ascobalt, nickel, tungsten, molybdenum, rhenium, titanium, tantalum,hafnium, zirconium, alloys thereof, or combinations thereof.

In one embodiment, metal-containing layer 316 may be formed by exposingsubstrate 300 to an activation solution during an electroless depositionprocess. In one example, metal-containing layer 316 may be formed byexposing substrate 300 to an activation process. In another example,metal-containing layer 316 may be formed by exposing substrate 300 to athermal process. In another example, metal-containing layer 316 may beformed by exposing substrate 300 to a silicidation process.

FIGS. 3H-3I illustrate substrate 300 before and after contact aperture310 is filled with metal contact material 320, during step 660 ofprocess 600 (FIG. 6). Metal contact material 320 is deposited onmetal-containing layer 316 within contact aperture 310. In analternative embodiment, cobalt-nickel stack material 330 may be formedon metal-containing layer 316, as illustrated in FIG. 4D by substrate400 that correlates to substrate 300 in FIG. 3I. Deposition processesfor depositing metal-containing layer 316 on substrate 300 are furtherdescribed below.

In another embodiment, FIGS. 3H and 3J illustrate substrate 300 atdifferent stages of process 600. SAM-layer 350 may be formed onsubstrate 300 during optional step 650, as depicted in FIG. 3J.SAM-layer 350 may be initially deposited over dielectric layer 304 andmetal-containing layer 316. In one example, SAM-layer 350 is depositedon metal-containing layer 316 containing a metallic surface. In anotherexample, SAM-layer 350 is deposited on metal-containing layer 316containing a metal silicide surface.

FIGS. 3J-3K illustrate substrate 300 before and after contact aperture310 is filled with metal contact material 320, during step 660 ofprocess 600. Metal contact material 320 may be deposited on SAM-layer350 within contact aperture 310. In an alternative embodiment,cobalt-nickel stack material 330 may be formed on SAM-layer 350, asillustrated in FIG. 4E by substrate 400 that correlates to substrate 300in FIG. 3K.

FIG. 7 depicts a flow graph of process 700 containing steps 710, 720,750, 760, and 780 that correlate to steps 610, 620, 650, 660, and 680 ofprocess 600. However, process 700 further provides the deposition ofcapping layer 318 during step 740. In one embodiment, capping layer 318may be deposited on substrate 300 as a barrier layer overmetal-containing layer 316, during step 740 of process 700. In oneexample, capping layer 318 may be deposited on SAM-layer 350 coveringmetal-containing layer 316 within contact aperture 310 (FIG. 3L).Thereafter, metal contact material 320 may be deposited on capping layer318 filling contact aperture 310 (FIG. 3M). In an alternativeembodiment, cobalt-nickel stack material 330 may be formed on cappinglayer 318, as illustrated in FIG. 4F by substrate 400 that correlates tosubstrate 300 in FIG. 3M.

In another example, capping layer 318 may be deposited directly onmetal-containing layer 316 within contact aperture 310 (FIG. 3N).Thereafter, in one aspect, metal contact material 320 may be depositedon capping layer 318 filling contact aperture 310 (FIG. 3O). In analternative embodiment, cobalt-nickel stack material 330 may be formedon capping layer 318, as illustrated in FIG. 4G by substrate 400 thatcorrelates to substrate 300 in FIG. 3O. In another aspect, SAM-layer 350may be deposited on capping layer 318 (FIG. 3P). Subsequently, metalcontact material 320 may be deposited on SAM-layer 350 covering cappinglayer 318 and filling contact aperture 310 (FIG. 3Q). In alternativeembodiments, cobalt-nickel stack material 330 may be formed on SAM-layer350 covering capping layer 318, as illustrated in FIG. 4H by substrate400 that correlates to substrate 300 in FIG. 3O. Deposition processes,including electroless deposition processes and solutions for depositingcapping layer 318 on substrate 300, are further described below.

Pretreatment processes

Wet Clean Processes

In one embodiment, substrate 300 may be exposed to a wet clean processto remove oxide surface 312 and to form exposed surface 314 during steps510, 610, or 710 of processes 500, 600, or 700. Substrate 300 may betreated by wet clean processes, such as an acidic cleaning process(e.g., a solution containing hydrochloric acid and hydrogen peroxideheld at elevated temperature, such as SC2 clean), a basic cleaningprocess (e.g., a solution containing ammonium hydroxide and hydrogenperoxide held at elevated temperature, such as SC1 clean), or a seriesof wet cleans containing both acidic and basic cleaning processes. In apreferred embodiment, substrate 300 is exposed to a SC1 solution (e.g.,TMAH and H₂O₂) to remove organic residues and other contaminants andsubsequently, exposed to a BOE solution (e.g., 0.5 M of TEA-HF solution)to remove native oxides.

A wet clean process may include dispensing a wet clean solution acrossor sprayed on the surface of substrate 300. The wet clean process may bean in situ process performed in the same processing cell as a subsequentelectroless deposition process. Alternatively, substrate 300 may be wetcleaned in a separate processing cell from the subsequent electrolessdeposition processing cell. A wet-clean pretreatment process may occurfor about 10 minutes or less, such as within a range from about 5seconds to about 5 minutes, preferably, from about 5 seconds to about 3minutes, more preferably, from about 10 seconds to about 2 minutes, andmore preferably, from about 15 seconds to about 1 minute. During thepretreatment process, the substrate is maintained at a temperaturewithin a range from about 15° C. to about 50° C., preferably, about roomtemperature (e.g., 20° C.). The wet-clean process may be performed in aTEMPEST™ wet-clean system, available from Applied Materials, Inc.,located in Santa Clara, Calif. Other examples of various wet-cleanprocesses that may be used to remove oxide surface 312 are furtherdescribed in commonly assigned U.S. Ser. No. 60/709,564 (APPM 9916.L05),filed Aug. 19, 2005, U.S. Ser. No. 60/703,538 (APPM 9916.L03), filedJul. 29, 2005, and U.S. Ser. No. 60/663,493 (APPM 9916L), filed Mar. 18,2005, which are all incorporated by reference herein in their entirety.

In one embodiment, oxide surface 312 is removed by a HF-last solution toform exposed surface 314 as a substantially oxide-free, silicon hydridesurface. In one example, the wet-clean process utilizes an HF-lastsolution containing water, HF and optional additives includingchelators, surfactants, reductants, other acids or combinations thereof.In one example, the hydrogen fluoride concentration of a wet-cleansolution may be within a range from about 10 ppm to about 5 wt %,preferably, from about 50 ppm to about 2 wt %, and more preferably, fromabout 100 to about 1 wt %, for example, about 0.5 wt %. In anotherembodiment, oxide surface 312 is removed during a liquid reductionprocess to form exposed surface 314 as a substantially oxide-free,silicon-containing surface.

SC1 and SC2 Processes

In one embodiment, substrate 300 containing oxide surface 312 may beexposed to a SC1 clean solution to remove contaminants, such as organicand inorganic residues and particulates during steps 510, 610, or 710 ofprocesses 500, 600, or 700. In one example, the SC1 clean solutioncontains hydrogen peroxide and at least one basic compound, such asammonium hydroxide, tetramethylammonium hydroxide, ethanolamine,diethanolamine, triethanolamine, derivatives thereof, salts thereof, orcombinations thereof. The substrate may be heated to a temperaturewithin a range from about 50° C. to about 100° C., preferably, fromabout 70° C. to about 90° C.

In another embodiment, substrate 300 containing oxide surface 312 may beexposed to a SC2 clean solution during steps 510, 610, or 710 ofprocesses 500, 600, or 700. In one example, the SC2 clean solutioncontains hydrogen peroxide and hydrogen chloride. The substrate may beheated to a temperature within a range from about 50° C. to about 100°C., preferably, from about 70° C. to about 90° C.

BOE Processes and Solutions

In another embodiment of a preclean process, buffered oxide etch (BOE)solutions and processes may be used to selectively remove native oxidesand other contaminants from substrate 300 during steps 510, 610, or 710of processes 500, 600, or 700. The BOE solutions generally containalkanolamine compounds and an etchant, such as hydrogen fluoride. In oneembodiment, the viscosity of the BOE solution may be adjusted by varyinga concentration ratio of at least two alkanolamine compounds. A BOEsolution having a viscosity within a range from about 10 cP to about 30cP has superior wetting properties on a substrate surface during aprocess to selectively remove native oxide layers therefrom.

In one embodiment, a method for selectively removing oxide surface 312to form exposed surface 314 on substrate 300. In one example, substrate300 may be exposed to a BOE solution containing about 0.5 M of TEA-HFsolution for about 25 seconds at about 20° C. In another example,substrate 300 may be exposed to a BOE solution containing about 0.5 M ofEA-HF solution for about 20 seconds at about 20° C. In another example,substrate 300 may be exposed to a BOE solution containing about 0.5 M ofDEA-HF solution for about 30 seconds at about 20° C. Thereafter, theexcess BOE solution is removed by spinning the substrate for about 10seconds.

In one embodiment, a composition of a BOE solution is provided whichincludes, by weight, a first alkanolamine compound at a concentrationwithin a range from about 0.5% to about 10%, a second alkanolaminecompound at a concentration within a range from about 0.5% to about 10%,hydrogen fluoride at a concentration within a range from about 0.5% toabout 10%, water at a concentration within a range from about 80% toabout 98%, a pH value within a range from about 3.5 to about 5, and aviscosity within a range from about 10 cP to about 30 cP.

In one example, the first alkanolamine compound is at a concentrationwithin a range from about 1% to about 5%, the second alkanolaminecompound is at a concentration within a range from about 1% to about 5%,the hydrogen fluoride is at a concentration within a range from about 1%to about 5%, the water is at a concentration within a range from about85% to about 95%, the pH value is within a range from about 3.8 to about4.8, and the viscosity is within a range from about 12 cP to about 28cP. In another example, the first alkanolamine compound is at aconcentration within a range from about 2% to about 3%, the secondalkanolamine compound is at a concentration within a range from about 2%to about 3%, the hydrogen fluoride is at a concentration within a rangefrom about 1% to about 3%, the water is at a concentration within arange from about 88% to about 94%, the pH value is within a range fromabout 3.5 to about 5, preferably, from about 4 to about 4.5, and theviscosity is less than about 50 cP, such as within a range from about 15cP to about 25 cP. In another example, the first alkanolamine compoundis at a concentration of about 3%, the second alkanolamine compound isat a concentration of about 2%, the hydrogen fluoride is at aconcentration of about 2%, the water is at a concentration of about 92%,the pH value is within a range from about 4 to about 4.5, and theviscosity is less than about 50 cP, such as within a range from about 15cP to about 25 cP.

In some examples, a weight ratio of the first alkanolamine compound tothe second alkanolamine compound is within a range from about 1 to about5, for example, about 1.5, or about 1.1. The first and secondalkanolamine compounds may be different alkanolamine compounds selectedfrom ethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA), orderivatives thereof. For example, the first alkanolamine compound may beDEA and the second alkanolamine compound may be TEA. In another example,the first alkanolamine compound is DEA the second alkanolamine compoundis EA. In another example, the first alkanolamine compound is TEA thesecond alkanolamine compound is EA. In other examples, the firstalkanolamine compound is DEA at a concentration to have the viscositywithin a range from about 15 cP to about 25 cP or at a concentration byweight within a range from about 1% to about 15%.

A BOE solution may contain a first alkanolamine and a secondalkanolamine compound at a weight ratio concentration to form aviscosity within a range from about 10 cP to about 30 cP, hydrogenfluoride at a concentration by weight within a range from about 0.5% toabout 10%, water at a concentration by weight within a range from about80% to about 98%, a pH value within a range from about 3.5 to about 5,and a viscosity within a range from about 10 cP to about 30 cP. Thefirst and second alkanolamine compounds may include EA, DEA, TEA, orother alkanolamine derivatives. In one example, the weight ratioconcentration of the first alkanolamine compound to the secondalkanolamine compound is within a range from about 1 to about 5, such asabout 1.5 or about 1.1. In another example, the viscosity of the BOEsolution is within a range from about 12 cP to about 28 cP, preferably,from about 15 cP to about 25 cP.

The BOE solution may contain a pH adjusting agent, such as hydrofluoricacid, additional alkanolamine compounds, sulfuric acid, ammoniumhydroxide, tetramethylammonium hydroxide, derivatives thereof, orcombinations thereof. In one example, the BOE solution contains the pHadjusting agent at a concentration to have a pH value within a rangefrom about 3.5 to about 5, preferably, from about 3.8 to about 4.8, andmore preferably, from about 4 to about 4.5.

In one example, the buffered oxide etch solution contains a firstalkanolamine compound at a concentration by weight within a range fromabout 0.5% to about 10%, a second alkanolamine compound at aconcentration by weight within a range from about 0.5% to about 10%,hydrogen fluoride at a concentration by weight within a range from about0.5% to about 10%, water at a concentration by weight within a rangefrom about 80% to about 98%, a pH value within a range from about 3.5 toabout 5, and a viscosity within a range from about 10 cP to about 30 cP.

In another embodiment, a composition of a BOE solution is provided whichincludes DEA at a concentration by weight within a range from about 0.5%to about 10%, TEA at a concentration by weight within a range from about0.5% to about 10%, HF at a concentration by weight within a range fromabout 0.5% to about 10%, water at a concentration by weight within arange from about 80% to about 98%, a pH value within a range from about3.5 to about 5 and a viscosity within a range from about 10 cP to about30 cP.

In one example, the composition of the buffered oxide etch solutioncontains the DEA at a concentration within a range from about 1% toabout 5%, the TEA at a concentration within a range from about 1% toabout 5%, the HF at a concentration within a range from about 1% toabout 5%, the water at a concentration within a range from about 85% toabout 95%, the pH value within a range from about 3.8 to about 4.8, andthe viscosity within a range from about 12 cP to about 28 cP. In anotherexample, the composition of the buffered oxide etch solution containsthe DEA at a concentration within a range from about 2% to about 3%, theTEA is at a concentration within a range from about 2% to about 3%, theHF is at a concentration within a range from about 1% to about 3%, thewater is at a concentration within a range from about 88% to about 94%,the pH value is within a range from about 4 to about 4.5, and theviscosity is within a range from about 15 cP to about 25 cP. In anotherexample, the composition of the buffered oxide etch solution containsthe DEA is at a concentration of about 3%, the TEA is at a concentrationof about 2%, the HF is at a concentration of about 2%, the water is at aconcentration of about 92%, the pH value is within a range from about 4to about 4.5, and the viscosity is within a range from about 15 cP toabout 25 cP. The weight ratio of the DEA to the TEA is within a rangefrom about 1 to about 5, preferably, the weight ratio is about 1.5 orless and the viscosity is about 23 cP.

In another embodiment, a method for selectively removing an oxide layerfrom a substrate surface is provided which includes providing asubstrate having a native oxide surface and a feature surface andexposing the substrate to a buffered oxide etch solution to remove thenative oxide surface while forming a native surface and preserving thefeature surface on the substrate. The BOE solution may contain DEA at aconcentration by weight within a range from about 0.5% to about 10%, TEAat a concentration by weight within a range from about 0.5% to about10%, HF at a concentration by weight within a range from about 0.5% toabout 10%, water at a concentration by weight within a range from about80% to about 98%, a pH value within a range from about 3.5 to about 5,and a viscosity within a range from about 10 cP to about 30 cP. The pHvalue of the BOE solution may be adjusted to a point of zero charge ofsilicon, such as within a range from about 4 to about 4.5. The BOEsolution may have a weight ratio of the DEA to the TEA within a rangefrom about 1 to about 5. In one example of the BOE solution, the weightratio is about 1.5 and the viscosity is about 23 cP.

The method further provides that substrate 300 is exposed to the BOEsolution for a time period within a range from about 10 seconds to about120 seconds, preferably, from about 15 seconds to about 60 seconds, forexample, about 30 seconds. Substrate 300 may be exposed to a rinsesolution subsequent to the BOE solution. Thereafter, a metal-containingmaterial, such as a barrier layer or a metal silicide layer, may bedeposited or formed on the native surface.

A wet clean solution may contain hydrogen fluoride and at least onebasic compound, such as ammonium hydroxide, tetramethylammoniumhydroxide, EA, DEA, TEA, derivatives thereof, salts thereof, orcombinations thereof. Examples of the wet clean solution include anEA-HF complex, a DEA-HF complex, a TEA-HF complex, a DEA-EA-HF complex,a DEA-TEA-HF complex, a TEA-EA-HF complex, derivatives thereof, saltsthereof, or combinations thereof. In one example, substrate 300 isexposed to a BOE solution containing about 0.5 M of TEA-HF solution forabout 25 seconds at about 20° C. Thereafter, the excess BOE solution isremoved by spinning the substrate for about 10 seconds.

Plasma Etch Process

In another embodiment, substrate 300 is exposed to a plasma etch processor a plasma clean process remove oxide surface 312 and to form exposedsurface 314 during steps 510, 610, or 710 of processes 500, 600, or 700.Also, the plasma etch process may be used to remove native oxides andother contaminants formed on exposed contact surfaces prior to severalprocesses described herein, such as an electroless deposition process.Surfaces exposed to the plasma etch process usually have an improveadhesion of subsequently deposited metal layers. The plasma etch processis performed in a chamber adapted to perform a chemical etch clean andin-situ anneal on substrates.

An exemplary plasma etch process for removing native oxides on a surfaceof the substrate using an ammonia (NH₃) and nitrogen trifluoride (NF₃)gas mixture performed within a plasma etch processing chamber will nowbe described. The plasma etch process begins by placing a substrate intoa plasma etch processing chamber. During processing, the substrate maybe cooled below 65° C., such as between 15° C. and 50° C. In anotherexample, the substrate is maintained at a temperature of between 22° C.and 40° C. Typically, the substrate support is maintained below about22° C. to reach the desired substrate temperatures.

The ammonia gas and nitrogen trifluoride gas are introduced into the dryetching chamber to form a cleaning gas mixture. The amount of each gasintroduced into the chamber is variable and may be adjusted toaccommodate, for example, the thickness of the oxide layer to beremoved, the geometry of the substrate being cleaned, the volumecapacity of the plasma and the volume capacity of the chamber body. Inone aspect, the gases are added to provide a gas mixture having at leasta 1:1 molar ratio of ammonia to nitrogen trifluoride. In another aspect,the molar ratio of the gas mixture is at least about 3 to about 1(ammonia to nitrogen trifluoride). Preferably, the gases are introducedin the dry etching chamber at a molar ratio of from about 1:1 (ammoniato nitrogen trifluoride) to about 30:1, more preferably, from about 5:1(ammonia to nitrogen trifluoride) to about 30:1. More preferably, themolar ratio of the gas mixture is of from about 5 to 1 (ammonia tonitrogen trifluoride) to about 10 to about 1. The molar ratio of the gasmixture may also fall between about 10:1 (ammonia to nitrogentrifluoride) and about 20:1. Alternatively, a pre-mixed gas mixture ofthe preferred molar ratio may be used during the plasma etch process.

A purge gas or carrier gas may also be added to the gas mixture. Anysuitable purge/carrier gas may be used, such as argon, helium, hydrogen,nitrogen, forming gas, or mixtures thereof. Typically, the overall gasmixture by volume of ammonia and nitrogen trifluoride is within a rangefrom about 0.05% to about 20%. The remainder of the process gas may bethe carrier gas. In one embodiment, the purge or carrier gas is firstintroduced into the chamber body before the reactive gases to stabilizethe pressure within the chamber body.

The operating pressure within the chamber body can be variable. Thepressure may be maintained within a range from about 500 mTorr to about30 Torr, preferably, from about 1 Torr to about 10 Torr, and morepreferably, from about 3 Torr to about 6 Torr. An RF power within arange from about 5 watts to about 600 watts may be applied to ignite aplasma of the gas mixture within the plasma cavity. Preferably, the RFpower is less than about 100 watts. More preferable is that thefrequency at which the power is applied is very low, such as less thanabout 100 kHz, and more preferably, within a range from about 50 kHz toabout 90 kHz.

The plasma energy dissociates the ammonia and nitrogen trifluoride gasesinto reactive species that combine to form a highly reactive ammoniafluoride (NH₄F) compound and/or ammonium hydrogen fluoride (NH₄F—HF)which reacts with the substrate surface. In one embodiment, the carriergas is first introduced into the dry etch chamber, a plasma of thecarrier gas is generated, and then the reactive gases, ammonia andnitrogen trifluoride, are added to the plasma.

Not wishing to be bound by theory, it is believed that the etchant gas,NH₄F and/or NH₄F—HF, reacts with the native oxide surface to formammonium hexafluorosilicate ((NH₄)₂SiF₆), ammonia, and water. Theammonia and water are vapors at processing conditions and removed fromthe chamber by a vacuum pump attached to the chamber. A thin film ofammonium hexafluorosilicate is left behind on the substrate surface.

The thin film of ammonium hexafluorosilicate on the substrate surfacemay be removed during a vacuum sublimation process. The process chamberradiates heat to dissociate or sublimate the thin film of ammoniumhexafluorosilicate into volatile SiF₄, NH₃, and HF products. Thesevolatile products are then removed from the chamber by the vacuum pumpattached to the system. In one example, a temperature of about 75° C. orhigher is used to effectively sublimate and remove the thin film fromthe substrate. Preferably, a temperature of about 100° C. or more isused, such as between about 115° C. and about 200° C. Once the film hasbeen removed from the substrate, the chamber is purged and evacuatedprior to removing the cleaned substrate.

A plasma cleaning processes may be performed using a vacuum precleanchamber, such as a SICONI™ Preclean chamber and process, both availablefrom Applied Materials, Inc., located in Santa Clara, Calif. Furtherdescription of a plasma-assisted dry etch chamber and plasma etchprocess that may be used by embodiment herein is disclosed in commonlyassigned U.S. Ser. No. 11/063,645, (8802), entitled “In-Situ Dry CleanChamber For Front End Of Line Fabrication,” filed on Feb. 22, 2005, andU.S. Ser. No. 11/192,993, (8707.P1), entitled “Integrated ElectrolessDeposition System,” filed on Jul. 29, 2005, which are herebyincorporated by reference in their entirety to the extent notinconsistent with the claimed invention.

Activation Processes

In other embodiments, substrate 300 may be exposed to an activationprocess to remove oxide surface 312 and to form exposed surface 314,suicide layer 315, or metal-containing layer 316, or combinationsthereof during steps 510, 610, or 710 of processes 500, 600, or 700. Inone embodiment, interconnect layer 302 contains exposed surface 314 hasan exposed silicon contact surface within contact aperture 310. Exposedsurface 314 may contain a pure silicon surface, a siliconhydride-terminus surface, or a mixture thereof. In another embodiment,interconnect layer 302 contains exposed surface 314 has an exposedsilicide contact surface within contact aperture 310. The exposedsilicide contact surface contains a silicide surface, such as a cobaltsilicide, a nickel silicide, a cobalt nickel silicide, a cobalt tungstensilicide, alloys thereof, or combinations thereof. As described byembodiments herein, exposed surface 314 containing an exposed silicidecontact surface, silicide layer 315, or metal-containing layer 316 maycontain at least one metal silicide material that contains cobalt,nickel, tungsten, molybdenum, rhenium, titanium, tantalum, hafnium,zirconium, alloys thereof, or combinations thereof.

In another embodiment, the activation process may be a liquid reductionprocess, whereas oxide surface 312 is exposed to a reducing solution toform exposed surface 314 during steps 510, 610, or 710 of processes 500,600, or 700. The reducing solutions may contain at least onemetal-reductant, such as a compound containing a variable-valence metal.Variable-valence metals are utilized as metal-reductants due to theavailability of electrons between redox states and include compounds ofTi³⁺/Ti⁴⁺, Fe²⁺/Fe³⁺, Cr²⁺/Cr³⁺ and Sn²⁺/Sn⁴⁺. Metal-reductantscontaining variable-valence metals may contain a variety of anionicligands including complexing agents and halides, such as chlorides,fluorides, bromides or iodides. Complexing agents that are useful mayhave functional groups that include carboxylic acids, dicarboxylicacids, polycarboxylic acids, amino acids, amines, diamines, polyamines,alkylamines, alkanolamines and alkoxyamines. Complexing agents mayinclude citric acid, glycine, ethylenediamine (EDA), monoethanolamine,diethanolamine (DEA), triethanolamine (TEA), derivatives thereof, saltsthereof or combinations thereof. In one embodiment, citric acid or acitrate salt is a preferred complexing agent within a reducing solution.For example, a reducing solution may contain titanium salts withcarboxylic acid ligands, such as a citrate.

Generally, the reducing solutions are formed in water by combining ametal halide (e.g., titanium chloride containing TiCl₃ and TiCl₄) with asalt containing a predetermined ligand (e.g., trisodium citrate) to forma metal complex or a metal salt that contains the predetermined ligand(e.g., titanium citrate) having a variable-valence state. The reducingsolution may further contain additives such as various chelators,surfactants, pH adjusting agents, or combinations thereof.Variable-valence metal compounds and reducing solutions are furtherdescribed in V. V. Sviridov et al., “Use of Ti(III) Complexes to reduceNi, Co, and Fe in Water Solution,” J. Phys. Chem., vol. 100, pp.19632-19635, (1996), M Majima et al., “Development of Titanium RedoxElectroless Plating Method,” SEI Technical Review, vol. 54, pp. 67-70,(June 2002), S. Nakao et al., “Electroless Pure Nickel Plating Processwith Continuous Electrolytic Regeneration System,” Surface and CoatingsTechnology, vols. 169-170(1), pp. 132-134., (Jun. 2, 2003), which areeach incorporated by reference to the extent not inconsistent with theclaimed aspects and description herein.

In an effort to remove oxide surface 312, substrate 300 is exposed to areducing solution for a predetermined time to remove the oxides fromexposed surface 314. The liquid reduction process may occur for about 5minutes or less, preferably within a range from about 1 second to about120 seconds, more preferably, from about 5 seconds to about 90 seconds.During the liquid reduction process, the substrate is heated to atemperature within a range from about 20° C. to about 150° C.,preferably, from about 50° C. to about 100° C. In one example, themetal-reductant may be a Ti³⁺ compound, such as titanium citrate. In analternative embodiment of a pretreatment process, substrate 300 isexposed to a plasma process for a predetermined time to reduce oxidesurface 312 and form exposed surface 314.

In another embodiment, the pretreatment process may be a vapordeposition process, whereas oxide surface 312 is exposed to a reducingvapor to form exposed surface 314 during steps 510, 610, or 710 ofprocesses 500, 600, or 700. The reductant may include borane, diborane,borane-alkylsulfides, such as borane-dimethylsulfide (BH₃.(CH₃)₂S),alkyboranes (e.g., ethylborane), phosphine, alkylposphines (e.g.,dimethylphosphine), silane, disilane, trisilane, alkylsilanes (e.g.,methylsilane), ammonia, hydrazine, hydrogen, derivatives thereof orcombinations thereof. Preferably, the reductant is diborane, phosphine,silane, hydrazine, hydrogen, or combinations thereof.

Cobalt Activation Process and Solution

In other embodiments, the activation process may be a silicidationprocess, whereas exposed surface 314 is exposed to an action solution toform metal-containing layer 316 during steps 510, 610, 620, 710, or 720of processes 500, 600, or 700. In one embodiment, an activation solutionto form metal-containing layer 316 containing a cobalt silicide materialon substrate 300 contains a cobalt source, a fluoride source, and ahypophosphite source. Useful cobalt sources include cobalt sulfate,cobalt chloride, cobalt fluoride, cobalt acetate, cobalt phosphate,other Co²⁺ compounds, derivatives thereof, hydrates thereof orcombinations thereof. In one example, cobalt sulfate heptahydrate(COSO₄.7H₂O) is used within the activation solution to formcobalt-containing materials. The activation solution may have a cobaltsource at a concentration within a range from about 1 mM to about 500mM, preferably, from about 1 mM to about 100 mM, more preferably, fromabout 5 mM to about 50 mM, and more preferably, from about 10 mM toabout 30 mM, for example, about 22 mM.

The activation solution further contains a fluoride source. Usefulfluoride sources include hydrogen fluoride, ammonium fluoride compounds,including alkylammonium fluoride compounds and metal fluoride compounds,including alkaline fluoride compounds, rare-earth fluoride compounds,transition metal fluoride compounds, or combinations thereof. Ammoniumfluoride compounds, alkylammonium fluoride compounds, and alkanolaminefluoride compounds may have a chemical formula of [R₄N][F], wherein eachR is independently a hydrogen (H), an alkyl group, such as methyl (—CH₃or Me), ethyl(—C₂H₅ or Et), propyl(—C₃H₇ or Pr), butyl(—C₄H₉ or Bu),amyl(—C₅H₁₁), an alcohol group, such as methanol (—CH₂OH), ethanol(—C₂H₂OH), propanol (—C₃H₆OH), butanol (—C₄H₈OH), pentanol (—C₅H₁₀OH),derivatives thereof, or combinations thereof. The activation solutionmay have a fluoride concentration within a range from about 1 mM toabout 1 M, preferably, from about 10 mM to about 400 mM, morepreferably, from about 20 mM to about 200 mM, and more preferably, fromabout 50 mM to about 120 mM, for example, about 83 mM.

In one embodiment, a fluoride source includes an alkanolamine fluoridecompound with a chemical formula of [(HO(CH₂)_(n))_(m)NH_(4-m)][F],wherein n=1, 2, 3, 4, or 5 and m=1, 2, 3, or 4, for example, anethanolammonium fluoride has a chemical formula[(HOCH₂CH₂)_(m)NH_(4-m)][F]. In one example, a fluoride source is amonoalkanolamine fluoride compound with a chemical formula of[(HO(CH₂)_(n))NH₃][F], wherein n=1, 2, 3, 4, or 5, for example,ethanolammonium fluoride (EA-HF) with a chemical formula of[(HOCH₂CH₂)NH₃][F]. In another example, a fluoride source is adialkanolamine fluoride compound with a chemical formula of[(HO(CH₂)_(n))₂NH₂][F], wherein n=1, 2, 3, 4, or 5, for example,diethanolammonium fluoride (DEA-HF) with a chemical formula of[(HOCH₂CH₂)₂NH₂][F]. In another example, a fluoride source is atrialkanolamine fluoride compound with a chemical formula of[(HO(CH₂)_(n))₃NH][F], wherein n=1, 2, 3, 4, or 5, for example,triethanolammonium fluoride (TEA-HF) with a chemical formula of[(HOCH₂CH₂)₃NH][F]. In other examples, the fluoride sources includeammonium fluoride ([H₄N][F]) and tetramethylammonium fluoride([Me₄N][F]). The fluoride compounds may be added as a fluoride salt ormay be formed to the activation solution. In one embodiment, a fluoridesource may be formed in situ by combining a basic compound to an acidiccompound, such as combining diethanolamine (DEA) and hydrogen fluoride(HF) to form diethanolammonium fluoride (DEA-HF). Therefore, theactivation solution may contain a fluoride compound and also acomplexing base to form the respective fluoride salt. The base, such asammonia, alkylamine compounds, alkanolamine compounds, or mixturesthereof, may be contained in the activation solution at a concentrationwithin a range from about 1 mM to about 1 M, preferably, from about 10mM to about 400 mM, more preferably, from about 20 mM to about 200 mM,and more preferably, from about 50 mM to about 120 mM, for example,about 80 mM.

In another embodiment, the activation solution may contain two, three ormore different alkanolamine fluoride compounds, alkanolamine compounds,other fluoride sources, hydrogen fluoride, salts thereof, or mixturesthereof. The viscosity of the activation solution may be adjusted byvarying a concentration ratio of at least two alkanolamine compounds. Anactivation solution having a viscosity within a range from about 10 cPto about 30 cP has superior wetting properties while activating asubstrate surface. In one example, a molar ratio of the firstalkanolamine compound to the second alkanolamine compound is within arange from about 1 to about 5, preferably, from about 1 to about 1.5,for example, about 1.2. The first and second alkanolamine compounds maybe different alkanolamine compounds selected from ethanolamine (EA),diethanolamine (DEA), triethanolamine (TEA), or derivatives thereof. Forexample, the first alkanolamine compound may be DEA and the secondalkanolamine compound may be TEA. In another example, the firstalkanolamine compound is DEA the second alkanolamine compound is EA. Inanother example, the first alkanolamine compound is TEA the secondalkanolamine compound is EA.

An activation solution further contains a reductant, such as ahypophosphite source. Useful hypophosphite sources include sodiumhypophosphite, potassium hypophosphite, lithium hypophosphite, calciumhypophosphite, ammonium hypophosphite, tetramethylammonium (TMAH)hypophosphite and other alkylammonium hypophosphites, derivativesthereof, or combinations thereof. Hypophosphite of sodium, potassium,ammonium, or alkylammonium may have the chemical formula ofM_(n)H_(3-n)PO₂, where n=1, 2, or 3 and M is sodium, potassium ammonium,alkylammonium (e.g., TMAH), derivatives thereof, or combinationsthereof. In one example, a preferred hypophosphite source is TMAHhypophosphite or sodium hypophosphite. The activation solution may havea hypophosphite concentration within a range from about 1 mM to about 1M, preferably, from about 10 mM to about 400 mM, more preferably, fromabout 20 mM to about 200 mM, and more preferably, from about 50 mM toabout 120 mM, for example, about 83 mM.

In one embodiment, a cobalt activation solution may be used to formmetal-containing layer 316. In one example, the activation solution maycontain a cobalt concentration within a range from about 1 mM to about100 mM, a fluoride concentration within a range from about 10 mM toabout 400 mM, and a hypophosphite concentration within a range fromabout 5 mM to about 150 mM. Preferably, an activation solution maycontain a cobalt concentration within a range from about 5 mM to about50 mM, a fluoride concentration within a range from about 20 mM to about200 mM, and a hypophosphite concentration within a range from about 10mM to about 80 mM. More preferably, an activation solution may contain acobalt concentration within a range from about 10 mM to about 30 mM, afluoride concentration within a range from about 50 mM to about 120 mM,and a hypophosphite concentration within a range from about 20 mM toabout 60 mM. In one example, an activation solution contains a cobaltconcentration of about 22 mM, a fluoride concentration of about 83 mM,and a hypophosphite concentration of about 43 mM.

In one example, an activation solution has a pH value of about 7 andcontains about 22 mM of a cobalt sulfate hexahydrate, about 70 mM ofDEA-HF, about 18 mM of HF, and about 43 mM of a TMAH-hypophosphite. Inanother example, an activation solution has a pH value of about 7 andcontains about 22 mM of a cobalt sulfate hexahydrate, about 70 mM ofTEA-HF, about 18 mM of HF, and about 43 mM of a TMAH-hypophosphite. Inanother example, an activation solution has a pH value of about 7 andcontains about 22 mM of a cobalt sulfate hexahydrate, about 70 mM ofDEA-TEA-HF (DEA:TEA molar ratio of 1.22), about 18 mM of HF, and about43 mM of a TMAH-hypophosphite.

Generally, the substrate may be exposed to an activation solution toform a cobalt silicide layer for a time period within a range from about1 second to about 90 seconds, preferably, from about 5 seconds to about60 seconds, and more preferably, from about 10 seconds to about 30seconds, for example, about 20 seconds. The substrate may be heated to atemperature within a range from about 70° C. to about 95° C.,preferably, from about 80° C. to about 85° C. during the activationprocess.

Self Assembled Monolayer and Capping Layer

Self Assembled Monolayer

In one embodiment, SAM-layer 350 (self-assembled-monolayer) may bedeposited on substrate 300 to provide further barrier protection betweenneighboring layers during steps 550, 650, or 750 of processes 500, 600,or 700. An example of a prototypical SAM material includes, but is notlimited to, aminopropyltriethoxy silane (APTES). A vapor depositionprocess may be used to form SAM-layer 350 from APTES. Furtherdescription of a process for depositing a SAM material is disclosed incommonly assigned U.S. Ser. No. 60/754,230, filed Dec. 27, 2005,(9916L.06), which is herein incorporated by reference in its entirety.

Substrate 300 may be exposed to a plasma treatment process prior todepositing SAM-layer 350, as described in embodiments herein, such asduring optional step 750 of process 700 (FIG. 7). A plasma treatmentprocess containing water, hydrogen, or combinations thereof forms asilanol (e.g., Si—OH) terminated surface for promoting strong adhesionof SAM-layer 350 to an underlying layer, such as dielectric layer 304,exposed surface 314, silicide layer 315, metal-containing layer 316,capping layer 318, and other surfaces and layers on substrate 300.

In one embodiment, SAM-layer 350 may be deposited on substrate 300covering exposed surface 314 and dielectric layer 304 (FIG. 3E). Metalcontact material 320 is formed over SAM-layer 350 (FIG. 3F).Subsequently, substrate 300 is exposed to a thermal process and silicidelayer 315 is formed at the interface between metal contact material 320and interconnect layer 302 (FIG. 3G). The portion of SAM-layer 350therebetween is decomposed and may incorporate carbon into silicidelayer 315.

In another embodiment, SAM-layer 350 may be deposited on substrate 300covering metal-containing layer 316 and dielectric layer 304 (FIG. 3J).In one example, metal contact material 320 is directly formed overSAM-layer 350 (FIG. 3K). In another example, capping layer 318 is formedover SAM-layer 350 prior to the deposition of metal contact material 320(FIG. 3L-3M). The portion of SAM-layer 350 formed at the interfacebetween metal contact material 320 and metal-containing layer 316 may bepreserved (FIG. 3K), but usually is decomposed and incorporates carboninto nearby layers, such as metal-containing layer 316 (FIG. 3M). Thecomposition of SAM-layer 350, the composition of neighboring layers, andthe subsequent process temperatures experienced by substrate 300determine the extent the durability or decomposition of SAM-layer 350.

In another embodiment, SAM-layer 350 may be deposited on substrate 300covering capping layer 318 and dielectric layer 304 (FIG. 3P) and metalcontact material 320 is directly formed over SAM-layer 350 (FIG. 3Q).

Capping Layer

Capping layer 318 may be formed or deposited on substrate 300, asdescribed in embodiments herein, such as during step 740 of process 700(FIG. 7). In one embodiment, a selective deposition process may be usedto form or deposit capping layer 318 over the exposed areas ofmetal-containing layer 316 (FIGS. 3L-3Q). The selective depositionprocess may include an electroless deposition process, a CVD process, aPE-CVD process, an ALD process, a PE-ALD process, a PVD process, orcombinations thereof. The selective process covers metal-containinglayer 316 while maintaining sidewalls of contact aperture 310 free ofdeposited material. Capping layer 318, as a barrier layer, eliminates orreduces atomic diffusion (e.g., silicon) into metal contact materials320 from metals or metal suicides contained within metal-containinglayer 316.

In one example, capping layer 318 may be selectively deposited by use ofan electroless deposition process. The electroless deposition processmay be used to form a layer that contains a binary alloy, a ternaryalloy, or a quaternary alloy. Capping layer 318 may contain cobaltboride (CoB), cobalt phosphide (CoP), nickel boride (NiB), nickelphosphide (NiP), cobalt tungsten phosphide (CoWP), cobalt tungstenboride (CoWB), nickel tungsten phosphide (NiWP), nickel tungsten boride(NiWB), cobalt molybdenum phosphide (CoMoP), cobalt molybdenum boride(CoMoB), nickel molybdenum phosphide (NiMoB), nickel molybdenumphosphide (NiMoP), nickel rhenium phosphide (NiReP), nickel rheniumboride (NiReB), cobalt rhenium boride (CoReB), cobalt rhenium phosphide(CoReP), alloys thereof, derivatives thereof, or combinations thereof.The film composition of the binary or ternary alloys can be preferablydesigned to have a resistivity within a range from about 1 μΩ-cm toabout 200 μΩ-cm.

Capping layer 318 containing a cobalt-tungsten alloy or anickel-containing material may be deposited during an electrolessdeposition process that utilizes either a pre-mixed solution or solutionprepared by an in-line mixing process that combines componentialsolutions. In one example, an electroless solution to deposit acobalt-tungsten alloy may contain a cobalt source, a tungsten source, acitrate source, a hypophosphite source, a borane reductant, and otheradditives. In another example, an electroless solution to deposit anickel-containing material may contain a nickel source, a citratesource, a borane reductant and other complexing agents and additives.Other electroless deposition solutions and processes useful fordepositing cobalt-tungsten alloys are further described in the commonlyassigned U.S. Ser. No. 10/967,919, entitled, “Selective Self-initiatingElectroless Capping of Copper with Cobalt-containing Alloys,” filed onOct. 18, 2004, and published as US 2005-0136193, which is incorporatedby reference to the extent not inconsistent with the claimed aspects anddescription herein.

Sequential Electroless Deposition Processes for Co—Ni Stack Material

In embodiment described herein, FIGS. 4A-4H depict substrate 400 havingcontact aperture 310 filled with cobalt-nickel stack material 330 duringsteps 560, 660, or 760 of processes 500, 600, or 700. Cobalt-nickelstack material 330 may be formed during a bottom-up electrolessdeposition process. Cobalt-nickel stack material 330 may be formed by asequential electroless deposition process containing at least twoelectroless solutions, such as a cobalt solution containing a cobaltsource and a nickel solution containing a nickel source. Cobalt-nickelstack material 330 is formed of sequential layers of at least two typesof materials, layers 322 and 324, wherein layers 322 may contain acobalt material and layers 324 may contain a nickel material or viceversa. Cobalt materials and nickel materials contained withincobalt-nickel stack material 330 may contain cobalt, nickel, tungsten,boron or phosphorus and include materials such as metallic cobalt,cobalt boride, cobalt phosphide, cobalt borophosphide, metallic nickel,nickel boride, cobalt tungsten boride, nickel phosphide, nickelborophosphide, nickel tungsten boride, derivatives thereof, alloysthereof, or combinations thereof.

In one example, cobalt-nickel stack material 330 on substrate 400 (FIG.4A) may be formed during a sequential electroless deposition process,instead of forming metal contact material 320 on substrate 300 (FIG.3C). Similarly, by substituting a non-sequential electroless depositionprocess for the sequential electroless deposition process, a variety ofalternative features may be formed on substrate 400. In another example,cobalt-nickel stack material 330 on substrate 400 (FIG. 4B) may beformed during a sequential electroless deposition process, instead offorming metal contact material 320 on substrate 300 (FIG. 3D). Otherexamples include substituting metal contact material 320 on substrate300 for cobalt-nickel stack material 330 on substrate 400, where FIG. 4Ccorrelates to FIG. 3G, FIG. 4D correlates to FIG. 3I, FIG. 4E correlatesto FIG. 3K, FIG. 4F correlates to FIG. 3M, FIG. 4G correlates to FIG.3O, and FIG. 4H correlates to FIG. 3Q. In one example, cobalt-nickelstack material 330 may be a graded contact plug by forming layers 322and 324 closer to interconnect layer 302 with a different compositionthan layers 322 and 324 that are further away from interconnect layer302.

Sequential electroless deposition processes contain a variety ofsequences for exposing a substrate to deposition solutions and rinsesolutions. FIG. 8 illustrates a flow chart of process 800 describing oneembodiment of a sequential electroless deposition process. Duringoptional step 810, a substrate may be exposed to a pretreatment processas described herein to remove oxide surfaces, form hydride surfaces,form metallic surfaces, form silicide surfaces, form a SAM material,form a capping layer, by pre-clean processes, activation processes,reduction processes, or combinations thereof.

FIG. 9A depicts a graph to illustrate periods of time for exposing asubstrate to solutions during an electroless process, such as process800. During step 820, a cobalt material is formed by exposing thesubstrate to a cobalt solution containing a cobalt source for a timeperiod between to and t₁. Generally, the cobalt material is deposited toform a layer with a thickness within a range from about a discontinuousatomic layer to about 100 Å, preferably, from about an atomic layer toabout 50 Å, and more preferably, from about 5 Å to about 30 Å. The timeperiod between t₀ and t₁ may be within a range from about 5 seconds toabout 5 minutes, preferably, from about 10 seconds to about 3 minutes,and more preferably, from about 30 seconds to about 2 minutes.

The substrate is exposed to a rinse solution during a rinse process fora time period between t₁ and t₂ during step 830. The rinse solution ispreferably water, such as deionized water. Alternatively, the rinsesolution may contain an additive, such as a surfactant, a chelator or amild reductant. The rinse process removes the remaining cobalt solutionand any byproducts. Generally, the time period between t₁ and t₂ iswithin a range from about 5 seconds to about 5 minutes, preferably, fromabout 10 seconds to about 3 minutes, and more preferably, from about 30seconds to about 2 minutes.

During step 840, a nickel material is formed by exposing the substrateto a nickel solution containing a nickel source for a time periodbetween t₂ and t₃. Generally, the nickel material is deposited to form alayer with a thickness within a range from about a discontinuous atomiclayer to about 100 Å, preferably, from about an atomic layer to about 50Å, and more preferably, from about 5 Å to about 30 Å. The time periodbetween t₂ and t₃ may be within a range from about 5 seconds to about 5minutes, preferably, from about 10 seconds to about 3 minutes, and morepreferably, from about 30 seconds to about 2 minutes.

The substrate is again exposed to the rinse solution during a rinseprocess for a time period between t₃ and t₄ during step 850. The rinsesolution may be the same solution as used during step 830 or the rinsesolution may be different, dependant on the specific chemistries of thecobalt and nickel solutions. The rinse process removes the remainingnickel solution and any byproducts. Generally, the time period betweent₃ and t₄ is within a range from about 5 seconds to about 5 minutes,preferably, from about 10 seconds to about 3 minutes, and morepreferably, from about 30 seconds to about 2 minutes.

Once the cobalt-nickel material is deposited to a predeterminedthickness, the sequential electroless process is complete at step 860.However, multiple cycles of steps 820, 830, 840, and 850 may be repeateduntil the cobalt-nickel material is formed with the predeterminedthickness. For example, a second cycle of steps 820, 830, 840, and 850may be completed during t₄-t₈ and a third cycle of steps 820, 830, 840,and 850 may be completed during t₈-t₁₂ (FIG. 9A). Usually, thecobalt-nickel material is deposited onto the substrate to fill any viasor apertures.

In other aspects, process 800 may be modified by rearranging or omittingprocess steps. For example, step 820 may include a nickel solution andnot a cobalt solution while step 840 includes a cobalt solution and nota nickel solution. In another example, steps 820 or 840 may by skippedduring a cycle. In an alternative embodiment, multiple layers of cobaltmaterial may be deposited on each other or multiple layers of nickelmaterial may be deposited on each other. A graded cobalt-nickel materialmay be formed by selectively manipulating the order or the amount oftime of process steps 820, 830, 840, and 850.

Therefore, in an alternative embodiment, in reference to FIGS. 4A-4H,the composition of layers 322 and 324 may vary throughout cobalt-nickelstack material 330, such as that layers 322 and 324 that are closer tointerconnect layer 302 have a different composition than layers 322 and324 that are further away from interconnect layer 302 (FIGS. 4A-4H).Electroless deposition processes that may be utilized to controlcomposition of cobalt-nickel materials formed during processes describedherein (e.g., processes 800 and 1000) are further disclosed in commonlyassigned U.S. Ser. No. 11/040,962, entitled “Method and Apparatus forSelectively Changing Thin Film Composition During Electroless Depositionin a Single Chamber,” filed on Jan. 22, 2005, and published as US2005-0181226, which is incorporated by reference to the extent notinconsistent with the claimed aspects and description herein.

FIGS. 9B-9D depict graphs to illustrate periods of time for exposing asubstrate to solutions during various permutations of the electrolessdeposition processes. Process 800 may be modified by omitting step 830(FIG. 9B), by omitting step 850 (FIG. 9C), or conducting steps 820 and840 during the same time and omitting either step 830 or step 850 (FIG.9D).

FIG. 10 illustrates a flow chart of process 1000 describing anotherembodiment of a sequential electroless deposition process, and FIG. 11depicts a graph to illustrate periods of time for exposing a substrateto solutions during an electroless deposition process, such as process1000. During optional step 1010, a substrate may be exposed to apretreatment process and/or activation process as described for step810.

A cobalt-nickel material may be formed by exposing a substrate to anincreasing amount of a cobalt solution while exposing the substrate to adecreasing amount of a nickel solution for a time period between t₀ andt₁ during a transition step. The cobalt-nickel material is deposited toform a layer with a thickness within a range from about a discontinuousatomic layer to about 100 Å, preferably, from about an atomic layer toabout 50 Å, and more preferably, from about 5 Å to about 30 Å. The timeperiod between t₀ and t₁ may be within a range from about 5 seconds toabout 5 minutes, preferably, from about 10 seconds to about 3 minutes,and more preferably, from about 30 seconds to about 2 minutes.

During step 1020, a cobalt material is formed by exposing the substrateto a cobalt solution for a time period between t₁ and t₂. The cobaltmaterial is deposited to form a layer with a thickness within a rangefrom about a discontinuous atomic layer to about 100 Å, preferably, fromabout an atomic layer to about 50 Å, and more preferably, from about 5 Åto about 30 Å. The time period between t₁ and t₂ may be within a rangefrom about 5 seconds to about 5 minutes, preferably, from about 10seconds to about 3 minutes, and more preferably, from about 30 secondsto about 2 minutes.

A cobalt-nickel material may be formed by exposing the substrate to adecreasing amount of a cobalt solution while exposing the substrate toan increasing amount of a nickel solution for a time period between t₂and t₃ during another transition step. The cobalt-nickel material isdeposited to form a layer with a thickness within a range from about adiscontinuous atomic layer to about 100 Å, preferably, from about anatomic layer to about 50 Å, and more preferably, from about 5 Å to about30 Å. The time period between t₂ and t₃ may be within a range from about5 seconds to about 5 minutes, preferably, from about 10 seconds to about3 minutes, and more preferably, from about 30 seconds to about 2minutes.

A nickel material may be formed by exposing the substrate to a nickelsolution for a time period between t₃ and t₄ during step 1030. Thenickel material is deposited to form a layer with a thickness within arange from about a discontinuous atomic layer to about 100 Å,preferably, from about an atomic layer to about 50 Å, and morepreferably, from about 5 Å to about 30 Å. The time period between t₃ andt₄ may be within a range from about 5 seconds to about 5 minutes,preferably, from about 10 seconds to about 3 minutes, and morepreferably, from about 30 seconds to about 2 minutes.

Once the cobalt-nickel material is deposited to a predeterminedthickness, the sequential electroless process may be complete at step1040. However, multiple cycles of steps 1020 and 1030 and transitionsteps are repeated until the cobalt-nickel material is formed with apredetermined thickness. For example, a second cycle of steps 1020 and1030 and transition steps may be completed during t₄-t₈ and a thirdcycle of steps 1020 and 1030 and transition steps may be completedduring t₈-t₁₂ (FIG. 10). Usually, the cobalt-nickel material isdeposited onto the substrate to fill any vias or apertures.

The substrate may be exposed to a chemical mechanical polishing (CMP)process prior to the pretreatment and deposition processes describedherein. Usually, the CMP process is conducted in a first processchamber, the nickel-containing layer or cobalt-tungsten alloy layer maybe deposited in a second process chamber and the first and secondprocess chambers are on the same CMP tool. In one example, the first andsecond process chambers may be in fluid communication to an in-linemixing system that combines stock solutions used in the pretreatmentprocess and/or the electroless deposition processes.

Nickel Electroless Process

In some embodiments, a nickel-containing material may deposited asmetal-containing layer 316 or metal contact material 320 on substrate300 during steps 560, 660, or 760 of processes 500, 600, or 700.Nickel-containing materials may be deposited as capping layers orfilling material by an electroless deposition process throughoutembodiments described herein. Nickel-containing materials includemetallic nickel, nickel boride, nickel phosphide, nickel boridephosphide, or other nickel alloys. The electroless deposition solutionto form nickel-containing materials is an aqueous solution thatgenerally contains a nickel source, a reductant, at least one complexingagent, a pH adjusting agent, and optional additives and surfactants. Anickel-containing material may be deposited by an electroless processutilizing either a pre-mixed electroless deposition solution or anin-line mixing process that combines solution components to generate theelectroless solution.

The nickel source within the electroless deposition solution may have aconcentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM. Nickel sources providenickel ions (e.g., Ni²⁺) dissolved within the electroless solution andlater reduced out as the deposited nickel-containing material. Usefulnickel sources include nickel sulfate, nickel chloride, nickel acetate,nickel phosphate, derivatives thereof, hydrates thereof, or combinationsthereof. In a preferred embodiment, nickel sulfate hexahydrate(NiSO₄.6H₂O) is used in the electroless solution to depositnickel-containing materials.

The reductant within the electroless deposition solution may have aconcentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM. Reductants provideelectrons to induce chemical reduction of the nickel ions that form anddeposit the nickel-containing material. Reductants may include organicreductants (e.g., formaldehyde or glyoxylic acid), hydrazine, organichydrazines (e.g., methyl hydrazine), hypophosphite sources (e.g.,hypophosphorous acid (H₃PO₂), ammonium hypophosphite((NH₄)_(4-x)H_(x)PO₂) and salts thereof), borane sources (e.g.,dimethylamine borane complex ((CH₃)₂NH.BH₃), DMAB), trimethylamineborane complex ((CH₃)₃N.BH₃), TMAB), tert-butylamine borane complex(^(t)BuNH₂.BH₃), tetrahydrofuran borane complex (THF.BH₃), pyridineborane complex (C₅H₅N.BH₃), ammonia borane complex (NH₃.BH₃), borane(BH₃), diborane (B₂H₆), derivatives thereof, complexes thereof, orcombinations thereof. In a preferred embodiment, DMAB is used as areductant in the electroless solution for depositing nickel-containingmaterials.

Chelators or complexing agents are in the electroless solution tocomplex nickel ions thereby stabilizing the solubility and reduction ofnickel ions. The complexing agents may have a concentration of about 2 Mor less, such as within a range from about 10 mM to about 500 mM,preferably, from about 50 mM to about 300 mM, and more preferably, fromabout 75 mM to about 200 mM, such as about 150 mM. Complexing agentsgenerally may have functional groups, such as carboxylic acids,dicarboxylic acids, polycarboxylic acids, amino acids, amines, diamines,polyamines, alkylamines, alkanolamines, or alkoxyamines. Complexingagents may include citric acid, citrates, glycolic acid, glycine,malonic acid, maleic acid, lactic acid, ethylenediaminetetraacetic acid(EDTA), ethylenediamine (EDA), triethylene tetramine (TETA),diaminoethane, ethanolamine (EA), diethanolamine (DEA), triethanolamine(TEA), hydroxylamine hydrochloride, ammonia, ammonium chloride,derivatives thereof, salts thereof, or combinations thereof. Usually,the electroless solution contains more than one complexing agent.Preferably, the electroless solution contains at least citric acid orcitrate salts, more preferably, the electroless solution also containsDEA, glycine, and/or lactic acid. In one example, the electrolesssolution contains about 45 mM of citric acid, about 16 mM of DEA, about5 mM of glycine, and about 85 mM of lactic acid.

A pH adjusting agent may be added to adjust the electroless solution toa pH value within a range from about 8 to about 10, preferably, fromabout 8.5 to about 10, and more preferably, from about 9.0 to about 9.5,such as about 9.2. The pH adjusting agent may be an acidic compound todecrease the pH value of the electroless solution and includehydrochloric acid, sulfuric acid, phosphoric acid, derivatives thereof,or combinations thereof. Alternatively, the pH adjusting agent may be abasic compound to increase the pH value of the electroless solution andinclude metal hydroxides, tetraalkylammonium hydroxides (e.g.,tetramethylammonium hydroxide ((CH₃)₄NOH, TMAH) or tetraethylammoniumhydroxide ((CH₃CH₂)₄NOH, TEAH)), ammonium hydroxide, DEA, TEA,derivatives thereof, or combinations thereof. The pH adjusting agent maybe dissolved in water prior to adjusting the pH value of the electrolesssolution. In one example, a 25 wt % aqueous solution of TMAH is used asa pH adjusting agent. In another example, both TMAH and DEA are used toadjust the pH value of an electroless solution.

The optional additives may include levelers, accelerators andsuppressors. Levelers within the electroless solution are used toachieve different deposition thickness as a function of levelerconcentration and feature geometry while depositing nickel-containingmaterials. The leveler within the electroless deposition solution mayhave a concentration within a range from about 20 ppb to about 600 ppm,preferably, from about 100 ppb to about 100 ppm. Examples of levelersthat may be employed in an electroless solution include, but are notlimited to alkylpolyimines and organic sulfonates, such as1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine,2-mercaptothiazoline, ethylene thiourea, thiourea, or derivativesthereof. The electroless deposition solution may contain brighteners oraccelerators and suppressors as alternative additives to provide furthercontrol of the deposition process. The role of accelerators is toachieve a smoothly deposited surface of the nickel-containing material.The accelerator within the electroless deposition solution has aconcentration within a range from about 20 ppb to about 600 ppm,preferably, from about 100 ppb to about 100 ppm. Accelerators that areuseful in an electroless solution for depositing nickel-containingmaterials may include sulfur-based compounds such asbis(3-sulfopropyl)disulfide (SPS), 3-mercapto-1-propane sulfonic acid(MPSA), aminoethane sulfonic acids, thiourea, derivatives thereof,combinations thereof. Suppressors are used to suppress nickel depositionby initially adsorbing onto underlying catalytic surfaces and thereforeblocking access to the catalyst of the reaction. Suppressors generallymay include polyethylene glycol (PEG), polypropylene glycol (PPG),polyoxyethylene-polyoxypropylene copolymer (POCP), benzotriazole (BTA),dipyridyl, dimethyl dipyridyl, derivatives thereof, or combinationsthereof. The suppressor within the electroless deposition solution has aconcentration within a range from about 20 ppb to about 600 ppm,preferably, from about 100 ppb to about 100 ppm.

The electroless solution may contain boric acid as an additionaladditive. Boric acid is added to provide additional buffering and tostabilize the composition of the solution. Boric acid is an oxidationby-product from the chemical reactions of borane reductants (e.g.,DMAB). Therefore, an electroless solution containing boric acid is morenormalized at the start of the deposition process since a less steepdissipation gradient exist as additional boric acid is formed from theborane reductant. Boric acid is preferably within the electrolessdeposition solution at concentration within a range from about 0.1 mM toabout 50 mM, preferably, from about 0.5 mM to about 5 mM, and morepreferably, from about 1 mM to about 3 mM, such as about 2 mM.

Also, an optional surfactant may be added to the electroless solution.The surfactant is a wetting agent to reduce the surface tension betweenthe electroless solution and the substrate surface. Surfactants aregenerally added to the electroless solution at a concentration of about1,000 ppm or less, preferably about 800 ppm or less, such as from about20 ppb to about 600 ppm. The surfactant may have ionic or non-ioniccharacteristics. A preferred surfactant includes dodecyl sulfates, suchas sodium dodecyl sulfate (SDS). Other surfactants that may be used inthe electroless deposition solution include glycol ether basedsurfactants (e.g., polyethylene glycol). For example, a glycol etherbased surfactants may contain polyoxyethylene units, such as TRITON®100, available from Dow Chemical Company. A nonylphenol ethoxylatesurfactant is useful in the electroless deposition solution, such asTERGITOL®, available from Dow Chemical Company or IGEPAL-630, availablefrom GAF Corporation. Other useful surfactants may contain phosphateunits, for example, sodium poly(oxyethylene)phenyl ether phosphate, suchas RHODAFAC® RE-610, available from Rhodia, Inc. The surfactants may besingle compounds or a mixture of compounds of molecules containingvarying length of hydrocarbon chains.

An electroless process to deposit nickel-containing materials mayutilize an in-line mixing process to form the electroless solution. Theprocess may contain the addition of two, three, four or morecomponential solutions to form the electroless solution. In one example,the electroless solution is formed by combining a buffered complexingsolution, a nickel-containing solution, a reducing solution and water,where each solution is a concentrate and water is added to reach apredetermined concentration of the final solution. In another example,the electroless solution is formed by combining a buffered complexingsolution, a nickel-containing solution and a reducing solution, whereeach of the solutions are pre-diluted and therefore do not requireadditional water. In another example, the electroless solution is formedby combining a buffered nickel-containing solution, a reducing solutionand water, where a buffered complexing solution and a nickel-containingsolution are combined to form the buffered nickel-containing solution.Further details of in-line mixing processes and componential solutionsare further described in the commonly assigned U.S. Ser. No. 10/967,919,entitled, “Selective Self-initiating Electroless Capping of Copper withCobalt-containing Alloys,” filed on Oct. 18, 2004, and published as US2005-0136193, which is incorporated by reference to the extent notinconsistent with the claimed aspects and description herein.

A buffered complexing solution usually contains water, at least onecomplexing agent, additives and a pH adjusting agent. The complexingagent within the buffered complexing solution is at a concentration fromabout 0.1 M to about 3 M, preferably, from about 0.2 M to about 2 M. Theadditive within the buffered complexing solution is at a concentrationfrom about 10 mM to about 1 M, preferably, from about 50 mM to about 500mM. The pH adjusting agent is at a concentration to provide the bufferedcomplexing solution with a pH value within a range from about 8 to about11, preferably, from about 9 to about 10, and more preferably, fromabout 9.2 to about 9.6, such as about 9.4. In one example, a bufferedcomplexing solution contains water, about 450 mM of DEA, about 300 mM ofcitric acid, about 150 mM of glycine, about 50 mM of boric acid and aconcentration of TMAH to adjust the pH value to about 9.4. In anotherexample, a buffered complexing solution contains water, about 1.15 M ofDEA, about 375 mM of citric acid, about 300 mM of glycine, about 100 mMof boric acid and a concentration of TMAH to adjust the pH value toabout 9.4. In another example, a buffered complexing solution containswater, about 330 mM of DEA, about 300 mM of citric acid, about 150 mM ofglycine, about 50 mM of boric acid and a concentration of TMAH to adjustthe pH value to about 9.4.

A nickel-containing solution usually contains water, a nickel source, atleast one complexing agent, and a pH adjusting agent. The nickel sourcewithin the nickel-containing solution is at a concentration from about50 mM to about 1 M, preferably, from about 100 mM to about 500 mM, suchas about 300 mM. The complexing agent within the nickel-containingsolution is at a concentration from about 0.2 M to about 2 M,preferably, from about 0.5 M to about 1 M. The pH adjusting agent is ata concentration to provide the nickel-containing solution with a pHvalue within a range from about 8 to about 11, preferably, from about8.5 to about 10, and more preferably, from about 9 to about 9.5, such asabout 9.2. In one example, a nickel-containing solution contains water,about 100 mM of citric acid, about 275 mM of nickel sulfate, about 567mM of 85% lactic acid and a concentration of TMAH to adjust the pH valueto about 9.2.

A reducing solution usually contains water, at least one reductant, atleast one complexing agent and a pH adjusting agent. The reductantwithin the reducing solution is at a concentration from about 10 mM toabout 500 mM, preferably, from about 50 mM to about 300 mM, such asabout 200 mM. The complexing agent within the reducing solution is at aconcentration from about 10 mM to about 200 mM, preferably, from about50 mM to about 150 mM, such as about 100 mM. The pH adjusting agent isat a concentration to provide the reducing solution with a pH valuewithin a range from about 8 to about 11, preferably, from about 9 toabout 10, and more preferably, from about 9.0 to about 9.4, such asabout 9.2. In one example, a reducing solution contains water, about 100mM of citric acid, about 204 mM of DMAB, and a concentration of TMAH toadjust the pH value to about 9.2.

The electroless solution is preferably formed by in-line mixing processthat combines various volumetric ratios of the buffered complexingsolution, the nickel-containing solution, the reducing solution andwater. In one example, one volumetric equivalent of a bufferedcomplexing solution, two volumetric equivalents of a nickel-containingsolution, two volumetric equivalents of a reducing solution, and fivevolumetric equivalents of deionized water are in-line mixed to form anelectroless solution. That is, the volumetric ratio of the bufferedcomplexing solution, the nickel-containing solution, the reducingsolution, and the deionized water is 1:2:2:5. In another example of anelectroless solution, a volumetric ratio of the buffered complexingsolution, the nickel-containing solution, the reducing solution, and thewater is 1:1:1:3. In a preferred example, the volumetric percentages ofthe buffered complexing solution, the nickel-containing solution, thereducing solution and the deionized water is about 3.5%, about 15%,about 20%, and about 61.5%, therefore, the volumetric ratio is about 1.0to about 4.3 to about 5.7 to about 17.6.

In one embodiment, an electroless solution contains: nickel sulfate witha concentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM; DMAB with aconcentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM; citric acid with aconcentration within a range from about 5 mM to about 200 mM,preferably, from about 10 mM to about 100 mM, and more preferably, fromabout 30 mM to about 60 mM, such as about 45 mM; DEA with aconcentration within a range from about 5 mM to about 100 mM,preferably, from about 10 mM to about 30 mM, such as about 16 mM;glycine with a concentration within a range from about 0.5 mM to about100 mM, preferably, from about 1 mM to about 50 mM, and more preferably,from about 2 mM to about 10 mM, such as about 5 mM; boric acid with aconcentration within a range from about 0.5 mM to about 50 mM,preferably, from about 1 mM to about 20 mM, and more preferably, fromabout 1 mM to about 5 mM, such as about 2 mM; lactic acid with aconcentration within a range from about 10 mM to about 300 mM,preferably, from about 20 mM to about 200 mM, and more preferably, fromabout 50 mM to about 150 mM, such as about 85 mM; TMAH with aconcentration to adjust the electroless solution to a have pH valuewithin a range from about 8 to about 11, preferably, from about 8.5 toabout 10, and more preferably, from about 9.0 to about 9.6, such asabout 9.2.

In one embodiment, citrate is a preferred complexing agent and ispresent in each componential solution, such as the buffered complexingsolution, the nickel-containing solution and the reducing solution.Citrate may be added as citric acid and/or as a citrate salt. Citrateplays an important role for buffering each of the individualcomponential solutions while being combined to form the platingsolution. Citrates generally have poor solubility in water at highconcentrations, while the componential solutions may have relativelyconcentrated solutions. If a substantial citrate concentration of thefinal electroless solution is desired, a single componential solutionmay not be capable of completely containing all the dissolved citrate.Therefore, the citrate may be dissolved in each componential solution toassure no formation of citrate precipitate, and subsequently combinedwith water forming the electroless solution at a final concentration.

The electroless deposition process may be conducted at a temperaturewithin a range from about 35° C. to about 120° C., preferably, fromabout 60° C. to about 100° C., and more preferably, from about 75° C. toabout 80° C. The water may be degassed, preheated and/or deionizedwater. Degassing the water reduces the oxygen concentration of thesubsequently formed electroless solution. An electroless solution with alow oxygen concentration (e.g., less than about 100 ppm) may be usedduring the deposition process. Preheated water allows forming theelectroless solution at a predetermined temperature just below thetemperature used to initiate the deposition process, thereby shorteningthe process time.

The processes described herein may be performed in an apparatus suitablefor performing an electroless deposition process (EDP). A suitableapparatus includes the SLIMCELL™ processing platform that is availablefrom Applied Materials, Inc., located in Santa Clara, Calif. TheSLIMCELL™ platform, for example, is an integrated system capable ofetching a native oxide within a wet-clean cell during a BOE process anddepositing cobalt-containing materials, cobalt-tungsten materials,cobalt-nickel materials, nickel-containing materials within an EDP cell.The SLIMCELL™ platform generally includes a wet-clean cell or etch celland one or more EDP cells as well as one or more pre-deposition orpost-deposition cell, such as spin-rinse-dry (SRD) cells or annealingchambers. Process systems, platforms, chambers, and cells useful for wetclean processes and electroless deposition processes, as describedherein, are further disclosed in commonly assigned U.S. Ser. No.10/059,572, entitled “Electroless Deposition Apparatus,” filed Jan. 28,2002, and published as US 2003-0141018, U.S. Ser. No. 10/965,220,entitled, “Apparatus for Electroless Deposition,” filed on Oct. 14,2004, and published as US 2005-0081785, U.S. Ser. No. 10/996,342,entitled, “Apparatus for Electroless Deposition of Metals onSemiconductor Wafers,” filed on Nov. 22, 2004, and published as US2005-0160990, U.S. Ser. No. 11/043,442, entitled, “Apparatus forElectroless Deposition of Metals on Semiconductor Wafers,” filed on Jan.26, 2005, and published as US 2005-0263066, U.S. Ser. No. 11/175,251,entitled, “Apparatus for Electroless Deposition of Metals onSemiconductor Wafers,” filed on Jul. 6, 2005, and published as US2005-0260345, U.S. Ser. No. 11/192,993, entitled, “IntegratedElectroless Deposition System,” filed on Jul. 29, 2005, and published asUS 2006-0033678, and U.S. Ser. No. 11/040,962, entitled, “Method andApparatus for Selectively Changing Thin Film Composition DuringElectroless Deposition in a Single Chamber,” filed on Jan. 22, 2005, andpublished as US 2005-0181226, which are each incorporated by referenceto the extent not inconsistent with the claimed aspects and descriptionherein.

Cobalt and Nickel Electroless Deposition Solutions and Processes Cobalt

In some embodiments, a cobalt material or a nickel material maydeposited as metal-containing layer 316 or metal contact material 320 onsubstrate 300 during steps 560, 660, or 760 of processes 500, 600, or700. In one embodiment, an electroless solution for depositing metalliccobalt contains: cobalt ions (Co²⁺) with a concentration within a rangefrom about 1 mM to about 100 mM, preferably, from about 5 mM to about 50mM, and more preferably, from about 10 mM to about 20 mM, such as about15 mM; hydrazine hydrate with a concentration within a range from about100 mM to about 2 M, preferably, from about 200 mM to about 1 M, andmore preferably, from about 300 mM to about 400 mM, such as about 500mM; citric acid or citrate salt with a citrate concentration within arange from about 5 mM to about 200 mM, preferably, from about 10 mM toabout 100 mM, and more preferably, from about 30 mM to about 70 mM, suchas about 50 mM; and an optional pH adjusting agent (e.g., TMAH) with aconcentration to adjust the electroless solution to a have pH valuewithin a range from about 10 to about 14, preferably, from about 11.5 toabout 13, and more preferably, from about 12.2 to about 12.8, such asabout 12.5. In one example, a pH value is about 11.5 or higher,preferably, about 12.0 or higher, and more preferably, about 12.5 orhigher. The electroless deposition process to deposit metallic cobaltmay be conducted at a temperature within a range from about 35° C. toabout 100° C., preferably, from about 60° C. to about 90° C., and morepreferably, from about 70° C. to about 80° C., such as about 75° C.

Cobalt Boride

In one embodiment, an electroless solution for depositing cobalt boridecontains: cobalt ions (Co²⁺) with a concentration within a range fromabout 1 mM to about 150 mM, preferably, from about 10 mM to about 100mM, and more preferably, from about 20 mM to about 80 mM, such as about35 mM; DMAB with a concentration within a range from about 1 mM to about100 mM, preferably, from about 5 mM to about 50 mM, and more preferably,from about 10 mM to about 40 mM, such as about 25 mM; chelating agentwithin a range from about 10 mM to about 500 mM, preferably, from about50 mM to about 300 mM, and more preferably, from about 75 mM to about250 mM, such as about 150 mM; ammonium fluoride within a range fromabout 1 mM to about 100 mM, preferably, from about 2 mM to about 50 mM,and more preferably, from about 5 mM to about 20 mM, such as about 11mM; and an optional pH adjusting agent (e.g., TMAH) with a concentrationto adjust the electroless solution to a have pH value within a rangefrom about 8 to about 11, preferably, from about 8.5 to about 10, andmore preferably, from about 9.0 to about 9.6, such as about 9.2. Theelectroless deposition process to deposit cobalt boride may be conductedat a temperature within a range from about 35° C. to about 100° C.,preferably, from about 70° C. to about 90° C., and more preferably, fromabout 75° C. to about 85° C., such as about 80° C.

In another embodiment, an electroless solution for depositing cobaltboride contains: cobalt sulfate with a concentration within a range fromabout 1 mM to about 150 mM, preferably, from about 10 mM to about 100mM, and more preferably, from about 20 mM to about 80 mM, such as about35 mM; DMAB with a concentration within a range from about 1 mM to about100 mM, preferably, from about 5 mM to about 50 mM, and more preferably,from about 10 mM to about 40 mM, such as about 25 mM; DEA within a rangefrom about 1 mM to about 300 mM, preferably, from about 10 mM to about100 mM, and more preferably, from about 30 mM to about 60 mM, such asabout 45 mM; citric acid or citrate salt with a citrate concentrationwithin a range from about 5 mM to about 500 mM, preferably, from about30 mM to about 300 mM, and more preferably, from about 50 mM to about150 mM, such as about 67 mM; lactic acid or lactate salt with a lactateconcentration within a range from about 1 mM to about 100 mM,preferably, from about 10 mM to about 50 mM, and more preferably, fromabout 15 mM to about 25 mM, such as about 19 mM; glycine within a rangefrom about 1 mM to about 100 mM, preferably, from about 5 mM to about 50mM, and more preferably, from about 10 mM to about 20 mM, such as about15 mM; boric acid within a range from about 0.5 mM to about 50 mM,preferably, from about 1 mM to about 10 mM, and more preferably, fromabout 2 mM to about 7 mM, such as about 5 mM; saccharin within a rangefrom about 0.02 mM to about 0.5 mM, preferably, from about 0.05 mM toabout 0.2 mM, and more preferably, from about 0.07 mM to about 0.15 mM,such as about 0.1 mM; ammonium fluoride within a range from about 1 mMto about 100 mM, preferably, from about 2 mM to about 50 mM, and morepreferably, from about 5 mM to about 20 mM, such as about 11 mM; and anoptional pH adjusting agent (e.g., TMAH) with a concentration to adjustthe electroless solution to a have pH value within a range from about 8to about 11, preferably, from about 8.5 to about 10, and morepreferably, from about 9.0 to about 9.6, such as about 9.2. Theelectroless deposition process to deposit cobalt boride may be conductedat a temperature within a range from about 35° C. to about 100° C.,preferably, from about 70° C. to about 90° C., and more preferably, fromabout 75° C. to about 85° C., such as about 80° C.

Cobalt Tungsten Boride

In one embodiment, an electroless solution for depositing cobalttungsten boride contains: cobalt ions (Co²⁺) with a concentration withina range from about 1 mM to about 100 mM, preferably, from about 5 mM toabout 50 mM, and more preferably, from about 10 mM to about 20 mM, suchas about 15 mM; tungstic acid or tungstate salt with a tungstateconcentration within a range from about 0.1 mM to about 10 mM,preferably, from about 0.5 mM to about 5 mM, and more preferably, fromabout 1 mM to about 3 mM, such as about 2 mM; DMAB with a concentrationwithin a range from about 1 mM to about 200 mM, preferably, from about10 mM to about 100 mM, and more preferably, from about 30 mM to about 50mM, such as about 40 mM; citric acid or citrate salt with a citrateconcentration within a range from about 5 mM to about 500 mM,preferably, from about 30 mM to about 300 mM, and more preferably, fromabout 50 mM to about 150 mM, such as about 100 mM; and an optional pHadjusting agent (e.g., TMAH) with a concentration to adjust theelectroless solution to a have pH value within a range from about 8 toabout 11, preferably, from about 8 to about 10, and more preferably,from about 8.5 to about 9.5, such as about 8.9. The electrolessdeposition process to deposit cobalt tungsten boride may be conducted ata temperature within a range from about 35° C. to about 100° C.,preferably, from about 60° C. to about 80° C., and more preferably, fromabout 65° C. to about 75° C., such as about 70° C.

Nickel Boride

In one embodiment, an electroless solution contains: nickel sulfate witha concentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM; DMAB with aconcentration within a range from about 1 mM to about 150 mM,preferably, from about 5 mM to about 100 mM, and more preferably, fromabout 10 mM to about 80 mM, such as about 40 mM; citric acid with aconcentration within a range from about 5 mM to about 200 mM,preferably, from about 10 mM to about 100 mM, and more preferably, fromabout 30 mM to about 60 mM, such as about 45 mM; DEA with aconcentration within a range from about 5 mM to about 100 mM,preferably, from about 10 mM to about 30 mM, such as about 16 mM;glycine with a concentration within a range from about 0.5 mM to about100 mM, preferably, from about 1 mM to about 50 mM, and more preferably,from about 2 mM to about 10 mM, such as about 5 mM; boric acid with aconcentration within a range from about 0.5 mM to about 50 mM,preferably, from about 1 mM to about 20 mM, and more preferably, fromabout 1 mM to about 5 mM, such as about 2 mM; lactic acid with aconcentration within a range from about 10 mM to about 300 mM,preferably, from about 20 mM to about 200 mM, and more preferably, fromabout 50 mM to about 150 mM, such as about 85 mM; TMAH with aconcentration to adjust the electroless solution to a have pH valuewithin a range from about 8 to about 11, preferably, from about 8.5 toabout 10, and more preferably, from about 9.0 to about 9.6, such asabout 9.2. The electroless deposition process to deposit nickel boridemay be conducted at a temperature within a range from about 35° C. toabout 100° C., preferably, from about 65° C. to about 90° C., morepreferably, from about 70° C. to about 85° C., and more preferably, fromabout 75° C. to about 80° C.

In another embodiment, an electroless solution for depositing nickelboride contains: nickel ions (Ni²⁺) with a concentration within a rangefrom about 1 mM to about 100 mM, preferably, from about 5 mM to about 50mM, and more preferably, from about 10 mM to about 20 mM, such as about15 mM; DMAB with a concentration within a range from about 1 mM to about200 mM, preferably, from about 10 mM to about 100 mM, and morepreferably, from about 30 mM to about 50 mM, such as about 40 mM; citricacid or citrate salt with a citrate concentration within a range fromabout 5 mM to about 300 mM, preferably, from about 10 mM to about 100mM, and more preferably, from about 40 mM to about 60 mM, such as about50 mM; lactic acid or lactate salt with a lactate concentration within arange from about 5 mM to about 300 mM, preferably, from about 10 mM toabout 100 mM, and more preferably, from about 40 mM to about 60 mM, suchas about 50 mM; and an optional pH adjusting agent (e.g., TMAH) with aconcentration to adjust the electroless solution to a have pH valuewithin a range from about 8 to about 11, preferably, from about 8 toabout 10, and more preferably, from about 8.5 to about 9.5, such asabout 8.9. The electroless deposition process to deposit nickel boridemay be conducted at a temperature within a range from about 35° C. toabout 100° C., preferably, from about 60° C. to about 80° C., and morepreferably, from about 65° C. to about 75° C., such as about 70° C.

Nickel Tungsten Boride

In one embodiment, an electroless solution for depositing nickeltungsten boride contains: nickel ions (Ni²⁺) with a concentration withina range from about 1 mM to about 100 mM, preferably, from about 5 mM toabout 50 mM, and more preferably, from about 10 mM to about 20 mM, suchas about 15 mM; tungstic acid or tungstate salt with a tungstateconcentration within a range from about 0.1 mM to about 10 mM,preferably, from about 0.5 mM to about 5 mM, and more preferably, fromabout 1 mM to about 3 mM, such as about 2 mM; DMAB with a concentrationwithin a range from about 1 mM to about 200 mM, preferably, from about10 mM to about 100 mM, and more preferably, from about 30 mM to about 50mM, such as about 40 mM; citric acid or citrate salt with a citrateconcentration within a range from about 5 mM to about 300 mM,preferably, from about 10 mM to about 100 mM, and more preferably, fromabout 40 mM to about 60 mM, such as about 50 mM; lactic acid or lactatesalt with a lactate concentration within a range from about 5 mM toabout 300 mM, preferably, from about 10 mM to about 100 mM, and morepreferably, from about 40 mM to about 60 mM, such as about 50 mM; and anoptional pH adjusting agent (e.g., TMAH) with a concentration to adjustthe electroless solution to a have pH value within a range from about 8to about 11, preferably, from about 8 to about 10, and more preferably,from about 8.5 to about 9.5, such as about 8.9. The electrolessdeposition process to deposit nickel tungsten boride may be conducted ata temperature within a range from about 35° C. to about 100° C.,preferably, from about 60° C. to about 80° C., and more preferably, fromabout 65° C. to about 75° C., such as about 70° C.

Cobalt Nickel Boride

In one embodiment, an electroless solution for depositing cobalt nickelboride contains: cobalt ions (Co²⁺) with a concentration within a rangefrom about 1 mM to about 100 mM, preferably, from about 5 mM to about 50mM, and more preferably, from about 10 mM to about 20 mM, such as about15 mM; nickel ions (Ni²⁺) with a concentration within a range from about1 mM to about 100 mM, preferably, from about 5 mM to about 50 mM, andmore preferably, from about 10 mM to about 20 mM, such as about 15 mM;DMAB with a concentration within a range from about 1 mM to about 200mM, preferably, from about 10 mM to about 100 mM, and more preferably,from about 30 mM to about 50 mM, such as about 40 mM; citric acid orcitrate salt with a citrate concentration within a range from about 5 mMto about 500 mM, preferably, from about 30 mM to about 300 mM, and morepreferably, from about 50 mM to about 150 mM, such as about 100 mM; andan optional pH adjusting agent (e.g., TMAH) with a concentration toadjust the electroless solution to a have pH value within a range fromabout 8 to about 11, preferably, from about 8 to about 10, and morepreferably, from about 8.5 to about 9.5, such as about 8.9. Theelectroless deposition process to deposit cobalt nickel boride may beconducted at a temperature within a range from about 35° C. to about100° C., preferably, from about 60° C. to about 80° C., and morepreferably, from about 65° C. to about 75° C., such as about 70° C.

Cobalt Nickel

In one embodiment, an electroless solution for depositing cobalt nickelcontains: cobalt ions (Co²⁺) with a concentration within a range fromabout 1 mM to about 100 mM, preferably, from about 5 mM to about 50 mM,and more preferably, from about 10 mM to about 20 mM, such as about 15mM; nickel ions (Ni²⁺) with a concentration within a range from about 1mM to about 100 mM, preferably, from about 5 mM to about 50 mM, and morepreferably, from about 10 mM to about 20 mM, such as about 15 mM;hydrazine hydrate with a concentration within a range from about 100 mMto about 2 M, preferably, from about 200 mM to about 1 M, and morepreferably, from about 300 mM to about 400 mM, such as about 500 mM;citric acid or citrate salt with a citrate concentration within a rangefrom about 5 mM to about 500 mM, preferably, from about 30 mM to about300 mM, and more preferably, from about 50 mM to about 150 mM, such asabout 100 mM; and an optional pH adjusting agent (e.g., TMAH) with aconcentration to adjust the electroless solution to a have pH valuewithin a range from about 10 to about 14, preferably, from about 11.5 toabout 13, and more preferably, from about 12.2 to about 12.8, such asabout 12.5. The electroless deposition process to deposit cobalt nickelmay be conducted at a temperature within a range from about 35° C. toabout 100° C., preferably, from about 60° C. to about 90° C., and morepreferably, from about 70° C. to about 80° C., such as about 75° C.

Cobalt Activation Solution

In one embodiment, a cobalt activation solution may be used to activatesilicon-containing surfaces, such as a silicon surface or a metalsilicide surface. The cobalt activation solution may contain a cobaltconcentration within a range from about 1 mM to about 100 mM, a fluorideconcentration within a range from about 10 mM to about 400 mM, and ahypophosphite concentration within a range from about 5 mM to about 150mM. Preferably, an activation solution may contain a cobaltconcentration within a range from about 5 mM to about 50 mM, a fluorideconcentration within a range from about 20 mM to about 200 mM, and ahypophosphite concentration within a range from about 10 mM to about 80mM. More preferably, an activation solution may contain a cobaltconcentration within a range from about 10 mM to about 30 mM, a fluorideconcentration within a range from about 50 mM to about 120 mM, and ahypophosphite concentration within a range from about 20 mM to about 60mM. In one example, an activation solution contains a cobaltconcentration of about 22 mM, a fluoride concentration of about 83 mM,and a hypophosphite concentration of about 43 mM.

In one embodiment, citrate is a preferred complexing agent and may bepresent in cleaning solutions, reducing solutions (e.g., Ti³⁺/T⁴⁺complexes), cobalt-containing solutions, nickel-containing solutions orcobalt-nickel-containing solutions. Citrate may be added as citric acidand/or as a citrate salt. Citrate plays an important role of bufferingthe aforementioned solutions.

A “substrate surface,” as used herein, refers to any substrate ormaterial surface formed on a substrate upon which film processing isperformed. For example, a substrate surface on which processing may beperformed include materials such as monocrystalline, polycrystalline, oramorphous silicon, strained silicon, silicon on insulator (SOI), dopedsilicon, fluorine-doped silicate glass (FSG), silicon germanium,germanium, gallium arsenide, glass, sapphire, silicon oxide, siliconnitride, silicon oxynitride, or carbon doped silicon oxides, such asSiO_(x)C_(y), for example, BLACK DIAMOND® low-k dielectric, availablefrom Applied Materials, Inc., located in Santa Clara, Calif. Substratesmay have various dimensions, such as 200 mm or 300 mm diameter wafers,as well as, rectangular or square panes. Embodiments as described hereinprovide processes to deposit metal-containing layers on many types ofsubstrates and surfaces. Substrates on which embodiments of theinvention may be useful include, but are not limited to semiconductorwafers, such as crystalline silicon (e.g., Si<100> or Si<111>), siliconoxide, strained silicon, silicon germanium, doped or undopedpolysilicon, doped or undoped silicon wafers, and patterned ornon-patterned wafers. Substrates made of glass or plastic, which, forexample, are commonly used to fabricate flat panel displays and othersimilar devices, may also be used during embodiments described herein.

While foregoing is directed to the preferred embodiment of theinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for depositing a material on a substrate, comprising:positioning a substrate within a process chamber, wherein the substratecomprises an aperture containing an exposed silicide contact surface;exposing the exposed silicide contact surface to a deposition solutionto form a metal contact material over the exposed silicide contactsurface during an electroless deposition process; and filling theaperture with the metal contact material by continuing the electrolessdeposition process.
 2. The method of claim 1, wherein the exposedsilicide contact surface comprises at least one metal selected from thegroup consisting of cobalt, nickel, tungsten, molybdenum, rhenium,titanium, tantalum, hafnium, zirconium, alloys thereof, and combinationsthereof.
 3. The method of claim 2, wherein the metal contact materialcomprises a material selected from the group consisting of nickel,nickel phosphide, nickel boride, cobalt, cobalt tungsten, cobalttungsten phosphide, cobalt tungsten boride, cobalt tungsten phosphideboride, cobalt nickel, cobalt phosphide, cobalt boride, cobalt nickelphosphide, cobalt nickel boride, derivatives thereof, alloys thereof,and combinations thereof.
 4. The method of claim 1, wherein a cappinglayer is deposited on the exposed silicide contact surface prior tofilling the aperture with the metal contact material.
 5. The method ofclaim 4, wherein the capping layer comprises a material selected fromthe group consisting of cobalt tungsten phosphide, cobalt tungstenboride, cobalt tungsten phosphide boride, derivatives thereof, alloysthereof, and combinations thereof.
 6. The method of claim 5, wherein thecapping layer is deposited during an electroless deposition process. 7.The method of claim 1, wherein the exposed silicide contact surface isexposed to a preclean process prior to depositing the metal contactmaterial thereon.
 8. The method of claim 7, wherein the substrate isexposed to a plasma to remove native oxides or contaminants from theexposed suicide contact surface during the preclean process.
 9. Themethod of claim 8, wherein a thin film is formed on the substrate by theplasma and the thin film is removed by a vacuum sublimation process. 10.The method of claim 8, further comprising exposing the substrate to theplasma and a process gas comprising a gas mixture of ammonia andnitrogen trifluoride.
 11. The method of claim 10, wherein the gasmixture has a molar ratio of the ammonia to the nitrogen trifluoridewithin a range from about 1:1 to about 30:1.
 12. The method of claim 7,wherein the preclean process is a wet clean process.
 13. The method ofclaim 12, wherein the wet clean process comprises exposing the substrateto a wet clean solution comprising hydrogen fluoride and a basiccompound selected from the group consisting of ammonium hydroxide,tetramethylammonium hydroxide, ethanolamine, diethanolamine,triethanolamine, derivatives thereof, salts thereof, and combinationsthereof.
 14. The method of claim 13, wherein the wet clean solutioncomprises an EA-HF complex, a DEA-HF complex, a TEA-HF complex, aDEA-EA-HF complex, a DEA-TEA-HF complex, a TEA-EA-HF complex,derivatives thereof, salts thereof, and combinations thereof.
 15. Themethod of claim 12, wherein the wet clean process comprises exposing thesubstrate to a wet clean solution comprising hydrogen peroxide and abasic compound selected from the group consisting of ammonium hydroxide,tetramethylammonium hydroxide, ethanolamine, diethanolamine,triethanolamine, derivatives thereof, salts thereof, and combinationsthereof.
 16. The method of claim 12, wherein the wet clean processcomprises exposing the substrate to a wet clean solution comprisinghydrogen peroxide and hydrogen chloride.
 17. A method for depositing amaterial on a substrate, comprising: positioning a substrate within aprocess chamber, wherein the substrate comprises an aperture containingan exposed silicon contact surface; forming a metal silicide layer onthe exposed silicon contact surface; and exposing the substrate to anelectroless deposition process to fill the aperture with a metal contactmaterial.
 18. The method of claim 17, wherein the metal silicide layercomprises at least one metal selected from the group consisting ofcobalt, nickel, tungsten, molybdenum, rhenium, titanium, tantalum,hafnium, zirconium, alloys thereof, and combinations thereof.
 19. Themethod of claim 17, wherein the metal contact material comprises amaterial selected from the group consisting of nickel, nickel phosphide,nickel boride, cobalt, cobalt tungsten, cobalt tungsten phosphide,cobalt tungsten boride, cobalt tungsten phosphide boride, cobalt nickel,cobalt phosphide, cobalt boride, cobalt nickel phosphide, cobalt nickelboride, derivatives thereof, alloys thereof, and combinations thereof.20. The method of claim 19, wherein the electroless deposition processcomprises sequentially exposing the substrate to a first electrolesssolution containing a cobalt source and to a second electroless solutioncontaining a nickel source.
 21. The method of claim 20, wherein thesubstrate is rinsed after each exposure of the first electrolesssolution and the second electroless solution.
 22. The method of claim21, wherein a process cycle of the sequential exposures of the first andsecond electroless solutions is repeated to form the metal contactmaterial as a cobalt-nickel stack material having a predeterminedthickness.
 23. The method of claim 17, wherein a capping layer isdeposited on the metal silicide layer prior to filling the aperture withthe metal contact material.
 24. The method of claim 23, wherein thecapping layer comprises a material selected from the group consisting ofcobalt tungsten phosphide, cobalt tungsten boride, cobalt tungstenphosphide boride, derivatives thereof, alloys thereof, and combinationsthereof.
 25. The method of claim 24, wherein the capping layer isdeposited during an electroless deposition process.
 26. The method ofclaim 17, wherein a self assembled monolayer is deposited within theaperture prior to forming the metal contact material.
 27. The method ofclaim 17, wherein the metal silicide layer is formed from the exposedsilicon contact surface by exposing the substrate to a metal-containingactivation solution.
 28. The method of claim 27, wherein themetal-containing activation solution comprises a cobalt source, afluoride source, and a hypophosphite source.
 29. The method of claim 17,wherein the metal silicide layer is exposed to a preclean process priorto depositing the metal contact material thereon.
 30. The method ofclaim 29, wherein the substrate is exposed to a plasma to remove nativeoxides or contaminants from the metal silicide layer during the precleanprocess.
 31. The method of claim 30, wherein a thin film is formed onthe substrate by the plasma and the thin film is removed by a vacuumsublimation process.
 32. The method of claim 30, further comprisingexposing the substrate to the plasma and a process gas comprising a gasmixture of ammonia and nitrogen trifluoride.
 33. The method of claim 29,wherein the preclean process is a wet clean process that providesexposing the substrate to a wet clean solution comprising hydrogenfluoride and a basic compound selected from the group consisting ofammonium hydroxide, tetramethylammonium hydroxide, ethanolamine,diethanolamine, triethanolamine, derivatives thereof, salts thereof, andcombinations thereof.
 34. The method of claim 33, wherein the wet cleansolution comprises an EA-HF complex, a DEA-HF complex, a TEA-HF complex,a DEA-EA-HF complex, a DEA-TEA-HF complex, a TEA-EA-HF complex,derivatives thereof, salts thereof, and combinations thereof.
 35. Themethod of claim 29, wherein the preclean process is a wet clean processthat provides exposing the substrate to a wet clean solution comprisinghydrogen peroxide and a basic compound selected from the groupconsisting of ammonium hydroxide, tetramethylammonium hydroxide,ethanolamine, diethanolamine, triethanolamine, derivatives thereof,salts thereof, and combinations thereof.
 36. A method for depositing amaterial on a substrate, comprising: positioning a substrate within aprocess chamber, wherein the substrate comprises an aperture containingan exposed silicide contact surface; and filling the aperture with acobalt-nickel stack material during an electroless deposition processcomprising sequentially exposing the substrate to a first electrolesssolution containing a cobalt source and to a second electroless solutioncontaining a nickel source.
 37. The method of claim 36, wherein thecobalt-nickel stack material comprises a first layer comprising amaterial selected from the group consisting of cobalt, cobalt phosphide,cobalt boride, cobalt tungsten, cobalt tungsten phosphide, cobalttungsten boride, cobalt tungsten phosphide boride, derivatives thereof,alloys thereof, and combinations thereof, and a second layer comprisinga material selected from the group consisting of nickel, nickelphosphide, nickel boride, derivatives thereof, alloys thereof, andcombinations thereof.
 38. A composition of a cobalt deposition solution,comprising: a cobalt source at a concentration within a range from about1 mM to about 150 mM; a reducing agent source at a concentration withina range from about 1 mM to about 100 mM; and a chelating agent source ata concentration within a range from about 10 mM to about 500 mM.
 39. Thecomposition of claim 38, further comprising: the cobalt source at aconcentration within a range from about 10 mM to about 100 mM; thereducing agent source at a concentration within a range from about 5 mMto about 50 mM; and the chelating agent source at a concentration withina range from about 50 mM to about 300 mM.
 40. The composition of claim39, further comprising: the cobalt source at a concentration within arange from about 20 mM to about 80 mM; the reducing agent source at aconcentration within a range from about 10 mM to about 40 mM; and thechelating agent source at a concentration within a range from about 75mM to about 250 mM.
 41. The composition of claim 40, further comprisingthe cobalt source at a concentration of about 35 mM, the reducing agentsource at a concentration of about 25 mM, and the chelating agent sourceat a concentration of about 150 mM.
 42. The composition of claim 38,wherein the chelating agent source is selected from the group consistingof citric acid, lactic acid, glycine, ethanolamine, diethanolamine,triethanolamine, salts thereof, derivatives thereof, and combinationsthereof.
 43. The composition of claim 42, wherein the reducing agentsource comprises dimethylamine-borane complex.
 44. The composition ofclaim 43, further comprising boric acid.
 45. The composition of claim38, further comprising saccharin.
 46. The composition of claim 38,further comprising ammonium fluoride or tetramethylammonium fluoride.47. The composition of claim 38, further comprising a pH value within arange from about 8 to about
 10. 48. The composition of claim 47, whereinthe pH value is about 9.2.
 49. A composition of a nickel depositionsolution, comprising: a nickel source at a concentration within a rangefrom about 1 mM to about 150 mM; a reducing agent source at aconcentration within a range from about 1 mM to about 150 mM; and achelating agent source at a concentration within a range from about 10mM to about 500 mM.
 50. The composition of claim 48, further comprising:the nickel source at a concentration within a range from about 5 mM toabout 100 mM; the reducing agent source at a concentration within arange from about 5 mM to about 100 mM; and the chelating agent source ata concentration within a range from about 50 mM to about 300 mM.
 51. Thecomposition of claim 50, further comprising: the nickel source at aconcentration within a range from about 10 mM to about 80 mM; thereducing agent source at a concentration within a range from about 10 mMto about 80 mM; and the chelating agent source at a concentration withina range from about 75 mM to about 200 mM.
 52. The composition of claim51, further comprising the nickel source at a concentration of about 40mM, the reducing agent source at a concentration of about 40 mM, and thechelating agent source at a concentration of about 150 mM.
 53. Thecomposition of claim 49, wherein the chelating agent source is selectedfrom the group consisting of citric acid, lactic acid, glycine,ethanolamine, diethanolamine, triethanolamine, salts thereof,derivatives thereof, and combinations thereof.
 54. The composition ofclaim 53, wherein the reducing agent source comprisesdimethylamine-borane complex.
 55. The composition of claim 54, furthercomprising boric acid.
 56. The composition of claim 49, furthercomprising a pH value within a range from about 8 to about
 10. 57. Thecomposition of claim 56, wherein the pH value is about 9.2.